Comparison of the distribution and nervous innervation of the sensilla on the labrum of gryllus bimaculatus and acheta domesticus orthoptera gryllidae and an account of their development in acheta domesticus


Carline, T.; Kubra, K.; Brown, V.K.; Beck, R.

International Journal of Insect Morphology and Embryology 13(2): 81-104

1984


The labra of Gryllus bimaculatus (De Geer) and Acheta domesticus (L.) (Orthoptera : Gryllidae) were studied to reveal the distribution and nervous innervation of the sensilla, in order to provide morphological evidence of their function. Employing scanning electron microscopy and light microscopy, 9 types of sensilla are reported in G. bimaculatus and 10 types in A. domesticus. Of these sensilla, types 1 — 4 have setae ranging in size from 5 — 420 gm in G. bimaculatus and from 3 — 470 gm in A. domesticus. Secretory pores, coeloconic pegs, basiconic pegs and campaniform sensilla have been recorded in both species, while sensilla ampullacea are only present in A. domesticus. The different types of sensilla are found in discrete groups on the posterior surface of the labrum, but they are more randomly distributed on the anterior surface. The detailed innervation of the sensilla was revealed by means of nickel chloride infusion, followed by intensification using Timm's sulphide —silver technique. The labra of both species are innervated by 2 major branches of the labral nerve. Each sensillum is usually innervated by a bipolar neurone, although some sensilla have been shown to be innervated by multiterminal neurones. The dimensions and shapes of the cell bodies and dendrites are provided and differences between the 2 species are identified. In general, the cell bodies and dendrites are larger in a bimaculatus than they are in A. domesticus. The development of the sensilla through the nymphal instars to the adult is reported for A. domesticus. It is shown that for some types of sensilla, (types 8 and 13), the number remains constant throughout the developmental period, in some (type 1), the adult complement of sensilla is attained in the early instars, for others, (types 2, 6, 7, 9 and 10), there is a steady increase throughout development, while in others (types 3 and 4), sudden increases occur at specific moults.

Int.
J.
Insect
Morphol.
&
Embryol.,
Vol.
13,
No.
2,
pp.
81
to
103,
1984.
Printed
in
Great
Britain.
0020
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Per
panion
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Ltd.
COMPARISON
OF
THE
DISTRIBUTION
AND
NERVOUS
INNERVATION
OF
THE
SENSILLA
ON
THE
LABRUM
OF
GRYLLUS
BIMACULATUS
(DE
GEER)
AND
ACHETA
DOMESTICUS
(L.)
(ORTHOPTERA
:
GRYLLIDAE),
AND
AN
ACCOUNT
OF
THEIR
DEVELOPMENT
IN
A.
DOMESTICUS
T.
CARLINE
Derbyshire
College
of
Higher
Education,
Kedleston
Road,
Derby
DE3
1GB,
U.K.
K.
KUBRA
and
V.
K.
BROWN
Department
of
Pure
and
Applied
Biology,
Imperial
College,
Prince
Consort
Road,
London
SW7
5BD,
U.K.
and
R.
BECK
Derbyshire
College
of
Higher
Education,
Kedleston
Road,
Derby
DE3
1GB,
U.K.
(Accepted
31
August
1983)
Abstract
—The
labra
of
Gryllus
bimaculatus
(De
Geer)
and
Acheta
domesticus
(L.)
(Orthoptera
:
Gryllidae)
were
studied
to
reveal
the
distribution
and
nervous
innervation
of
the
sensilla,
in
order
to
provide
morphological
evidence
of
their
function.
Employing
scanning
electron
microscopy
and
light
microscopy,
9
types
of
sensilla
are
reported
in
G.
bimaculatus
and
10
types
in
A.
domesticus.
Of
these
sensilla,
types
1
4
have
setae
ranging
in
size
from
5
420
gm
in
G.
bimaculatus
and
from
3
470
gm
in
A.
domesticus.
Secretory
pores,
coeloconic
pegs,
basiconic
pegs
and
campaniform
sensilla
have
been
recorded
in
both
species,
while
sensilla
ampullacea
are
only
present
in
A.
domesticus.
The
different
types
of
sensilla
are
found
in
discrete
groups
on
the
posterior
surface
of
the
labrum,
but
they
are
more
randomly
distributed
on
the
anterior
surface.
The
detailed
innervation
of
the
sensilla
was
revealed
by
means
of
nickel
chloride
infusion,
followed
by
intensification
using
Timm's
sulphide
—silver
technique.
The
labra
of
both
species
are
innervated
by
2
major
branches
of
the
labral
nerve.
Each
sensillum
is
usually
innervated
by
a
bipolar
neurone,
although
some
sensilla
have
been
shown
to
be
innervated
by
multiterminal
neurones.
The
dimensions
and
shapes
of
the
cell
bodies
and
dendrites
are
provided
and
differences
between
the
2
species
are
identified.
In
general,
the
cell
bodies
and
dendrites
are
larger
in
a
bimaculatus
than
they
are
in
A.
domesticus.
The
development
of
the
sensilla
through
the
nymphal
instars
to
the
adult
is
reported
for
A.
domesticus.
It
is
shown
that
for
some
types
of
sensilla,
(types
8
and
13),
the
number
remains
constant
throughout
the
developmental
period,
in
some
(type
1),
the
adult
complement
of
sensilla
is
attained
in
the
early
instars,
for
others,
(types
2,
6,
7,
9
and
10),
there
is
a
steady
increase
throughout
development,
while
in
others
(types
3
and
4),
sudden
increases
occur
at
specific
moults.
Index
descriptors
(in
addition
to
those
shown
in
the
title):
Scanning
electron
microscopy,
iontophoresis,
sensilla
basiconica,
sensilla
coeloconica,
campaniform
sensilla,
sensilla
ampullacea.
INTRODUCTION
MOST
work
on
the
sensilla
of
the
mouthparts
of
the
Orthoptera
has
focused
on
the
Acrididae,
with
the
Gryllidae
receiving
relatively
little
attention.
Liu
and
Leo
(1960)
and
81
82
T.
CARLINE,
K.
KUBRA,
V. K.
BROWN
and
R.
Beck
Thomas
(1966)
briefly
described
the
sense
organs
on
the
mouthparts,
including
the
labrum,
of
Locusta
migratoria
manilensis
and
Schistocerca
gregaria
respectively.
The
fine
structure
of
the
contact
chemoreceptors
on
the
posterior
surface
and
of
the
campaniform
sensilla
on
the
anterior
surface
of
the
labrum
in
Locusta
migratoria
was
examined
by
Sinior
et
al.
(1968),
Louveau
(1972)
and
Cook
(1972,
1977,
1979).
Marshall
(1947)
also
described
some
of
the
sensilla
on
the
labrum
of
Melanoplus
femur
rubrum,
and
the
mouthparts
of
Xenocheila
zarudnyi
were
thoroughly
investigated
by
Chapman
(1966).
A
survey
of
the
abundance and
distribution
of
mouthpart
sensilla
of
106
species
of
Acridoidea
was
carried
out
by
Chapman
and
Thomas
(1978).
In
comparison,
there
are
few
major
works
on
the
Gryllidae.
Narula
(1968)
described
the
gross
morphology
of
the
head
capsule
and
its
appendages
in
Gryllodes
sigillatus,
while
JILT
recently,
Kubra
(1978)
has
made
a
comprehensive
study
of
the
mouthparts
and
eeding
behaviour
of
A.
domesticus.
Much
of
her
work
on
the
labrum
sensilla
is
presented
here.
Fudalewicz-Niemczyk
and
his
co-workers
in
Poland
have
also
studied
A.
domesticus,
in
respect
of
the
mouthparts
of
the
last
larval
instar
(Rokiszewska
and
Fudalewicz-Niemczyk,
1974),
the
adult
clypeo-labrum
(Urvoy
et
al.,
1978)
and
a
subsequent
comparison
with
Carausius
morosus
(Urvoy
et
al.,
1981).
However,
although
these
works
recognise
certain
groups
of
sensilla
they
give
no
quantitative
data.
In
G.
bimaculatus
only
the
maxillary
palp
has
received
any
detailed
investigation
(Klein
and
Muller,
1978;
Klein,
1981,
1982).
Although
the
distribution
of
sense
organs
on
the
labrum
has
received
some
attention,
details
of
their
nervous
innervation
is
not
nearly
so
well
known.
In
the
Acrididae,
Louveaux
(1972)
and
Mordue
(1975)
have
investigated
this
to
some
extent
in
Locusta
migratoria
and
Schistocerca
gregaria
respectively,
while
in
the
Gryllidae
reference
is
made
to
the
nervous
innervation
of
sensilla
in
the
final
larval
instar
of
A.
domesticus
by
Rokiszewska
and
Fudalewicz-Niemczyk,
(1974).
This
paper
presents
a
detailed
examination
of
the
types
of
sensilla,
their
distribution
and
nervous
innervation
on
the
labrum
of
adults
of
both
sexes
of
the
field
cricket,
G.
bimaculatus
and
compares
this
with
the
labrum
of
adults
of
the
house
cricket,
A
domesticus.
In
addition,
the
paper
describes
in
A.
domesticus,
the
development of
the
sensilla
through
the
nymphal
instars
to
the
condition
shown
by
the
adult,
a
virtually
unexplored
subject.
The
function
of
certain
mouthpart
receptors
in
relation
to
feeding
has
been
considered,
amongst
others,
by
Haskell
and
Schoonhoven
(1969)
in
Schistocerca
gregaria
and
in
Locusta
migratoria
migratorioides
where
electrophysiological
techniques
have
been
used
to
analyse
the
responses
of
chemoreceptors
and
mechanoreceptors
on
the
labrum.
The
present
paper
forms
a
vital
prerequisite
for
this
type
of
work
to
be
extended
to
the
Gryllidae
and
such
behavioural
investigations
will
be
reported
in
a
subsequent
paper.
MATERIALS
AND
METHODS
Crickets
were
reared
in
an
insectary
at
a
temperature
of
34°C,
a
12L
:
12D
light
regime
and
an
RH
of
70%.
Breeding
stocks
were
maintained
in
groups
of
about
50
insects
in
plastic
aquaria.
Food
was
supplied
in
the
form
of
commercial
rabbit
pellets
and
water
was
continually
available
in
gravel
-filled
petri
dishes
or
water
-soaked
cotton
wool
pads.
The
labra
of
both
sexes
of
each
species
were
examined,
and
those
of
all
nymphal
instars
in
A.
domesticus.
Each
labrum
was
removed
from
the
head,
just
dorsal
to
the
clypeo-labral
suture,
boiled
for
15
min
in
10%
caustic
potash
and
rinsed
thoroughly
in
distilled
water.
After
dehydration,
the
labra
were
mounted
in
Euparal.
The
position
of
the
sensilla
was
plotted
with
the
aid
of
a
camera
lucida
fitted
to
a
Wild
M5
stereoscopic
microscope.
Comparison
of
the
Distribution
and
Nervous
Innervation
of
Sensilla
83
Labra
from
newly
moulted
adult
crickets
were
used
to
investigate
the
nervous
innervation
of
the
sensilla;
the
low
pigmentation
of
the
integument
and
the
thinner,
softer
cuticle
facilitating
microscopic
examination.
Study
of
the
distribution
of
neurones
was
based
on
whole
mounts
stained
intravitally
with
methylene
blue
and
on
heavy
metal
iontophoresis.
A
0.4%
stock
solution
of
methylene
blue
was
prepared
in
the
physiological
solution
developed
by
Moulins
(1971).
The
pH
was
adjusted
to
5
7.
Using
a
microsyringe,
0.2
ml
of
the
solution
was
injected
through
the
neck
membrane
and
a
further
0.2
ml
injection
given
15
min
later.
Specimens
were
left
for
30
min,
after
which
the
head
was
severed
from
the
rest
of
the
body
and
fixed
in
8%
cold
ammonium
molybdate
for
24
48
hr.
After
staining,
the
required
parts
were
dissected
under
saline.
For
heavy
metal
iontophoresis,
the
labral
nerve
was
dissected
out
under
saline
and
backfilled
using
a
2.0%
nickel
chloride
solution
(Strausfield
and
Obermyer,
1976),
for
12
hr
at
6°C.
The
preparations
were
then
washed
in
saline
and
transfered
to
a
solution
of
rubeanic
acid,
(saturated
to
75%
in
75%
alcohol)
for
15
min
(Quicke
and
Brace,
1979).
Following
this
treatment,
the
intensification
procedure
of
Bacon
and
Altman
(1977)
was
followed,
the
silver
deposit
being
carefully
checked
using
a
binocular
microscope.
This
process
usually
took
30
min
to
1
hr.
Following
intensification, the
preparations
were
washed
in
distilled
water,
dehydrated
slowly
for
12
hr,
cleaned
in
methyl
salicylate
and
mounted
in
Canada
Balsam.
After
intensification,
neurone
profiles
appeared
black
on
a
straw
coloured
or
light
brown
background.
For
scanning
electron
microscopy
(SEM),
labra
from
freshly
killed
specimens
were
again
used.
Initially
they
were
washed
in
distilled
water
containing
a
trace
of
detergent
to
remove
the
wax.
They
were
then
rinsed
several
times
in
distilled
water
to
remove
the
detergent
and
then
passed
through
the
alcoholic
grades
(50%
100%)
and
finally
into
acetone
or
amyl
acetate.
The
labra
were
then
transfered
to
a
critical
point
drying
apparatus.
After
2
hr,
the
labra
were
placed
in
anhydrous
silica
gel
mixed
with
cobalt
chloride
and
mounted
on
a
stub
using
colloidal
silver.
Finally,
they
were
each
coated
with
gold
palladium
alloy
(Nei
and
Fujikawa,
1977)
in
a
splutter
coater.
All
figures
and
SEM
micrographs
are
based
on
adult
female
insects,
except
where
otherwise
stated,
and
at
least
10
replicates
were
used
for
data
given
in
Tables
2
and
3.
RESULTS
AND
DISCUSSION
Gross
morphology
of
the
labrum
The
general
organisation
of
the
labrum
is
similar
in
both
species.
It
forms
an
upper
lip
to
the
preoral
food
cavity
and
is
a
broad
almost
symmetrical,
freely
moveable
plate.
The
term
anterior
is
used
to
describe
the
outer
surface
of
the
labrum,
whilst
the
inner,
epipharyngeal
surface
is
termed
posterior.
The
labrum
is
anteriorly
convex
and
is
attached
to
the
distal
margin
of
the
clypeus
by
a
flexible
transverse
membrane.
The
junction
with
the
clypeus
is
included
in
this
study.
The
posterior
surface
is
concave
and
fits
closely
over
the
mandibles.
The
distal
edge
of
the
labrum
is
notched
somewhat
to
the
right
of
the
midline.
Two
less
heavily
pigmented
strips
divide
the
anterior
surface
of
the
labrum
incompletely
into
median
and
lateral
areas
and
a
transverse
sulcus
forms
the
ventral
limit
of
a
well-defined
rectangular
area.
Two
curved
sclerotized
bars
divide
the
epipharyngeal
surface
into
a
median
and
two
lateral
areas
(Fig.
1).
The
position
of
these
is
seen
on
the
anterior
surface
as
the
pigmented
strips
already
mentioned.
These
bars
are
also
found
in
the
locust
(Chapman,
1966;
Thomas,
1966).
Cook
(1944)
refers
to
them
as
fimbriate
strips,
while
Reitschel
(1953)
in
his
study
of
the
labrum
of
immature
A.
domesticus
refers
to
them
as
"Verstarkungsleiste"
(
=
strengthening
rods).
Their
function
appears
to
be
to
strengthen
the
anterior
part
of
the
head
capsule.
In
the
lateral
angle
of
the
epipharyngeal
wall,
between
the
labrum
and
the
clypeus,
there
are
2
small
sclerotized
areas,
the
tormae
(Fig.
1),
to
which
the
adductor
muscles
of
the
labrum
are
attached.
A
small
ridge,
known
as
the
intertorma,
is
present
on
the
epipharyngeal
side
between
the
tormae,
and
serves
as
the
site
of
insertion
of
the
compressor
muscles
of
the
mandible
in
A.
domesticus
(Kubra,
1978).
Types
of
sensilla
The
description
of
sensilla
is
based
on
the
earlier
work
of
Kubra
(1978)
in
which
13
types
on
the
mouthparts
of
A.
domesticus
were
identified
based
on
their
external
form.
84
T.
CARI
INE,
K.
KUBRA,
V.
K.
BROWN
and
R.
BECK
Torma
Sclerotised
Bar
0.5mm
Al
t10
r
-
Ne-•
).
15)
1
1,5
, '
7
b
0.5mm
•::
Ag
tg
Al
t10
A2
t
10
Intertorma
A3
tg
tg
A10t4
Ag
t3
A5
t10
A11
t4
A6
t3
A
7
t
6
hair
fringe
Ag
t10
A2
t10
A3
tg
A
10t4
A4t3
Agt
3
A5t10
Agt3
A11t4
A7
t6
FIG.
1.
Distribution
of
sensilla
on
posterior
surface
of
labrum
of
(a)
G.
bimaculatus
and
(b)
A.
domesticus.
Types
5,
11
and
12
are
omitted
in
this
investigation
since
they
do
not
occur
on
the
labrum
in
either
species.
Type
13
is
also
absent
in
G.
bimaculatus.
In
addition
to
the
sensilla
there
are
numerous
microtrichia
and
some
elaborate
cuticular
sculpturing.
Table
1
gives
the
length
of
the
setae
in
types
1
4,
these
being
the
only
types
with
setae
of
any
appreciable
length.
Type
1
(t,).
Sensilla
with
the
longest
setae
but
of
variable
length.
These
sensilla
are
thin
relative
to
their
length
and
in
G.
bimaculatus
they
tend
to
be
longer
and
to
have
a
more
pronounced
socket
than
in
A.
domesticus.
In
both
species
they
are
scattered
over
the
anterior
surface
of
the
labrum
rather
than
forming
a
compact
group.
Type
2
(t
2
).
These
sensilla
have
setae
which
are
shorter
than
type
1
and
have
a
spiral
sculpturing
in
G.
bimaculatus
but
not
in
A.
domesticus.
In
both
species
they
are
found
on
the
anterior
surface
of
the
labrum
in
2
lateral
areas
associated
with
type
3
sensilla.
Comparison
of
the
Distribution
and
Nervous
Innervation
of
Sensilla
85
TABLE
1.
LENGTH
OF
SETAE
FROM
TYPE
1
-
4
SENSILI
A
Species
Type
of
Number
Standard
sensilla
measured
Mean
(gm)
error
Range
(gm)
G.
bimaculatus
1
50
260.41
±
9.22
180
-
420
2
50
130.40
±
4.12
95
-
180
3
55
43.60
±
2.91
5
-
95
4
53
160.21
±11.21
50
-
380
A.
domesticus
1
50
214.14
±
8.45
145
-
470
2
50
92.26
±
4.10
50
-
145
3
52
25.09
±
2.74
3
-
47
4
54
131.22
±
9.65
47
-
326
Type
3
(t
:
Fig.
2).
Sensilla
with
setae
which
are
always
less
than
96
gm
in
G.
bimaculatus
and
48
gm
in
A.
domesticus
but
include
sensilla
with
very
short,
slender
setae
that
may
be
level
with
the
surface
of
the
cuticle,
extend
just
above
it,
or
remain
below
it.
In
both
species,
these
sensilla
are
scattered
all
over
the
anterior
surface
of
the
labrum,
but
they
are
confined
to
discrete
areas
on
the
posterior
surface.
Type
4
(t,
:
Fig.
6).
Sensilla
with
a
thick
rigid
wall.
These
are
extremely
variable
in
size
in
both
species
and
have
sockets
with
protective
projections.
A
group
of
type
4
sensilla
is
present
on
the
posterior
surface
of
the
labrum.
Type
6
(t
6
).
Campaniform
sensilla,
which
are
mostly
spindle
shaped.
They
vary
in
length
(range
8
-
10.5
gm
in
G.
bimaculatus,
4
-
14
µm
in
A.
domesticus)
and
breadth
(range
4.8
-
6.5
gm
in
G.
bimaculatus,
2.1
-
7.5
pm
in
A.
domesticus).
They
are
situated
on
the
posterior
surface
of
the
labrum
in
discrete
groups.
Type
7
(t7
:
Fig.
7).
These
are
referred
to
as
secretory
pores
by
Arnold
(1974)
and
plate
organs
by
Slifer
(1970).
When
seen
with
the
light
microscope,
they
consist
of
a
shallow
depression
with
a
small
notch
on
the
proximal
border.
In
G.
bimaculatus
they
range
in
length
from
8.2
-
9.8
pm,
whilst
in
A.
domesticus
they
are
always
less
than
8
pm.
They
occur
on
the
anterior
surface
of
the
labrum.
Type
8
(t
8
:
Fig.
3).
These
sensilla
are
coeloconic
pegs
with
sunken
sockets
and
stout
peg
-shaped
setae.
The
thickness
of
the
seta
is
relatively
constant
throughout
its
length,
but
is
slightly
more
depressed
in
its
socket
in
G.
bimaculatus.
They
are
found
on
the
posterior
surface
of
the
labrum
and
vary
in
socket
diameter
(5
-
8µm
in
G.
bimaculatus,
4.2
-
7.5
gm
in
A.
domesticus).
In
A.
domesticus,
they
are
larger
in
size
than
the
other
coeloconic
sensilla
found
on
the
posterior
surface
of
the
labrum
(type
10),
but
in
G.
bimaculatus
they
are
smaller.
Type
9
(t
9
:
Fig.
4).
Sensilla,
which
are
basiconic
pegs.
In
G.
bimaculatus
all
these
sensilla
possess
a
rather
raised
socket
and
the
setae
are
slightly
dented
at
the
tip.
In
A.
domesticus,
however,
there
is
slight
variation
in
the
form
of
the
setae.
One
form
has
wavy
setae,
which
arise
from
a
sunken
socket,
while
the
other
has
stout
setae,
which
are
broadest
at
their
distal
end.
In
both
species
they
are
found
on
the
posterior
surface
of
the
labrum.
86
T.
CARL
INE,
K.
KUBRA,
V.
K.
BROWN
and
R.
BE(
I,
Type
10
(t,
,,
:
Fig.
5).
These
are
round,
coeloconic
pegs
with
a
depression
in
the
centre,
which
is
even
visible
under
the
light
microscope.
The
diameter
of
the
socket
varies
from
7.5
10.5
µm
in
G.
bimaculatus
to
3.0—
6.2
I.tm
in
A.
domesticus.
Projections
of
variable
form
arise
from
the
depressed
sockets.
These
sensilla
are
present
on
the
posterior
surface
of
the
labrum
in
both
species.
Type
13
(t,
3
).
These
are
absent
in
G.
bimaculatus.
In
A.
domesticus
they
are
flask
-
shaped
sensilla
that
are
often
called
sensilla
ampullacea
owing
to
their
shape.
The
depth
of
the
cavity
varies
from
22
25
ttm,
while
the
diameter
is
7.6
7.8
p.tm.
They
are
found
on
the
distal
part
of
the
anterior
surface
of
the
labrum.
Distribution
and
abundance
of
sensilla
types
In
the
2
species
investigated,
both
surfaces
of
the
labrum
are
well
supplied
with
sensilla.
Those
on
the
anterior
surface
are
scattered
more
or
less
randomly
(Fig.
8),
while
on
the
posterior
surface
they
are
arranged
in
discrete
groups
of
different
types
(Fig.
1:
referred
to
as
groups
A,
A
„).
Table
2
gives
the
abundance
of
each
type
of
sensilla
on
the
2
labral
surfaces,
while
Table
3
gives
the
precise
numbers
of
sensilla
associated
with
the
discrete
groups.
Thus,
in
the
text
only
approximate
numbers
occurring
in
the
groups
are
cited.
In
both
species
the
anterior
surface
of
the
labrum
is
well
supplied
with
sensilla
of
types
3
and
7
with
a
much
smaller
number
of
types
1
and
2
(Fig.
8).
Type
3
sensilla
are
more
numerous
on
the
anterior
surface
of
A.
domesticus,
but
in
both
species
this
type
is
widely
distributed.
Type
7
are
also
generally
distributed
in
G.
bimaculatus,
but
occur
mainly
on
the
lateral
areas
of
the
labrum
in
A.
domesticus.
In
this
respect,
type
2
are
rather
similar
in
distribution
although
only
relatively
few
are
present.
In
G.
bimaculatus
type
7
sensilla
are
also
found
in
2
distinct
areas,
each
of
8
10
sensilla,
one
on
each
side
of
the
notch.
The
type
1
sensilla
tend
to
be
arranged
in
pairs
although
unpaired
sensilla
of
this
type
may
occasionally
be
present.
In
G.
bimaculatus
one
unpaired
and
2
pairs
of
type
1
sensilla
are
situated
in
the
central
part
of
the
labrum,
whilst
in
A.
domesticus
3
pairs
are
situated
in
the
central
part,
with
another
3
pairs
occurring
on
the
weakly
sclerotized
distal
zone.
The
distal
end
of
the
labrum
is
notched
and
is
furnished
with
a
double
fringe
of
hairs
in
both
species.
However,
in
addition,
in
G.
bimaculatus
4
pairs
of
the
type
1
sensilla
are
located
around
the
notch
area,
whereas
in
A.
domesticus
2
pairs
of
the
type
13
sensilla
are
located
one
on
each
side
of
the
notch.
The
posterior
surface
of
the
labrum
may
be
subdivided
into
different
regions
or
fields
containing
groups
of
sensilla.
Adults
of
both
sexes
show
a
similar
distribution
of
sensilla,
though
minor
differences
in
numbers
do
occur.
Field
I.
This
represents
the
area
at
the
distal
end
of
the
clypeus
and
bears
3
groups
of
sensilla,
A,
,
A,
and
A,
(Fig.
1).
In
G.
bimaculatus
group
A
9
occurs
in
a
central
position
as
2
sub
-groups,
one
on
each
side
of
a
central
longitudinal
furrow,
whereas
in
A.
domesticus
the
2
small
sub
-groups
occur
one
above
each
torma.
Each
sub
-group
normally
consists
of
6
7
type
8
sensilla
in
G.
bimaculatus
and
of
around
17
type
10
sensilla
in
A.
domesticus,
although
in
the
latter
the
number
differs
slightly
between
the
sexes.
In
both
species
group
A,
is
also
sub
-divided
into
2
groups,
one
on
each
side
of
the
midline.
There
are
41
sensilla
in
each
sub
-group
in
G.
bimaculatus
and
approximately
48
in
A.
domesticus.
These
sensilla
are
type
10
sensilla
and
are
probably
comparable
to
the
Comparison
of
the
Distribution
and
Nervous
Innervation
of
Sensilla
87
3
t
Et#
p
4
'
111
4
1
."
---
7-
7
-.6
5
pm
"
4
0.
t
9
2
pm
0
FIGS
2-7.
Scanning
electron
micrographs
of
sensilla
types.
FIG.
2.
t,
(G.
bimaculatus).
x
6,000.
FIG.
3.
t,
(G.
bimaculatus).
x
9,000.
FIG.
4.
t.
(G.
bimaculatus).
x
9,000.
FIG.
5.
t,
0
(G.
bimaculatus).
x
4,000.
FIG.
6.
t,
(A.
domesticus).
x
1,000.
FIG.
7.
t,
(A.
domesticus).
x
9,000.
41m
88
T.
CARLINE,
K.
KUBRA,
V.
K.
BROWN
and
R.
BECK
a
I
I
0.5mm
0.5mm
e
0.5mm
0.5MM
t3
h
0.5MM
t
1
3
0.5mm
0.5mm
0.5mm
FIG.
8.
Distribution
of
certain
types
of
sensilla
on
anterior
surface
of
labrum
of
(a)
(d)
G.
bimaculatus,
(e)
(h)
A.
domesticus.
A,
group
of
Thomas
(1966).
Group
A,
is
located
in
a
medial
position
below
the
two
A,
sub
-groups.
This
group
consists
of
type
10
sensilla,
25
30
in
G.
bimaculatus,
with
the
surrounding
cuticular
plates
or
tiles
encroaching
on
to
the
socket
(this
encroachment
may
be
due
to
the
considerable
folding,
which
occurs
here
at
the
clypeo-labral
junction),
and
12
14
in
A.
domesticus,
with
sockets
slightly
larger
in
diameter
than
those
in
the
A,
group.
Lateral
to
the
A,
and
A2
groups
of
sensilla,
and
just
medial
to
the
tips
of
the
tormae,
are
2
large
areas
of
fine
hairs
or
microtrichia.
These
hairs,
which
extend
from
here
into
the
lateral
areas
of
field
II
between
the
type
4
sensilla
and
the
sclerotized
bar,
are
cuticular
processess
without
sockets
and
probably
have
a
purely
mechanical
function,
directing
food
particles
to
the
sensilla
of
groups
A,
and
A,
prior
to
swallowing.
In
G.
bimaculatus
TABLE
2.
ABUNDANCE
OF
SENSILLA
TYPES
ON
THE
ANTERIOR
AND
POSTERIOR
SURFACES
OF
THE
I
ABRUNI
OF
G.
bitttaCtdattlY
AND
A.
domesticus.
Type
t,
t,
t,
t,
t,
t,
t,
t,
t,,
t,,
G.
bimaculatus
Anterior
13
26
346
104
Male
Posterior
220
201
18
22
16
128
Anterior
13
25
334
111
Female
{
Posterior
236
196
15
24
15
131
A.
domesticus
Anterior
12
24
581
91
4
Male
Posterior
252
196
22
11
27
150
13
26
577
98
4
Female
{Anterior
Posterior
240
194
21
13
24
150
Values
are
means
expressed
to
the
nearest
whole
number.
Comparison
of
the
Distribution
and
Nervous
Innervation
of
Sensilla
8
TABLE
3.
NUMBER
OF
SENSILLA
IN
GROUPS
ON
THE
POSTERIOR
SURFACE
OF
THE
LABRUM
IN
ADULT
G.
bimaculatus
AND
A.
domesticus
Group
A,
G.
bimaculatus
Male
Female
A.
domesticus
Male
Female
1
41.3±1.41
41.1±1.21
42.3±0.81
41.8±0.93
)49.6±1.63
7.6±1.87
1
47.8±1.13
47.8±1.43
A, A, A,
A,
A,
A,
A, A,
A,
0
A„
27.1±1.61*
12.4±1.31
8.6±0.21
21.4±4.81
6.4±3.06
88.3±4.91
6.1±1.12
65.3±6.02
31.7±2.10
13.4±1.84
8.4±0.32
25.4±4.31
9.1±3.14
84.4±4.01
7.3±1.61
71.9±6.31
29.9±2.81
29.5±2.50*
14.7±1.36
9.4±0.78
26.0±0.89
6.3±0.51
76.8±9.82
7.0±1.12 96.3±8.49
29.8±1.30
14.4±0.89
9.2±0.83
26.6±0.54
6.6±0.61
80.5±8.98
6.2±1.01
99.9±9.31
29.5±2.41
14.2±1.42
5.6±0.24
10.2±0.14
10.4±0.32
26.4±1.80
14.2±1.39
88.0±4.33
16.8±0.58
61.2±2.10
36.4±0.81
13.2±0.58
6.4±0.24
11.4±0.51
10.4±0.32 25.6±0.81
13.8±1.24
92.2±4.26
18.6±0.68
62.1±1.44
37.1±1.24
12.8±0.46
6.3±0.17
10.0±0.33
10.5±0.34
32.2±1.17
10.5±0.55
79.2±1.15
16.7±0.61
60.9±1.79
36.9±0.98
12.5±0.34
6.7±0.17
10.0±0.37
10.5±0.29
31.5±0.99
10.3±0.76
77.7±0.97
17.1±0.63
61.1±1.11
36.2±0.84
Upper
value
=
right
side;
lower
value
=
left
side;
*whole
surface;
given
as
mean
±
standard
error.
T.
CARLINE,
K.
KUBRA,
V.
K.
BROWN
and
R.
BECK
Comparison
of
the
Distribution
and
Nervous
Innervation
of
Sensilla
91
these
hairs
are
single
or
double
pointed
but
in
A.
domesticus
trifid
hairs
have
also
been
identified.
Chapman
(1966)
has
found
similar
hairs
on
the
posterior
surface
of
the
clypeo-
labrum
in
X.
zarudnyi
although
Thomas
(1966)
does
not
record
their
presence
in
S.
gregaria.
Field
II.
This
field
starts
below
the
intertorma
and
is
enclosed
by
the
sclerotized
bars
(Fig.
1).
In
G.
bimaculatus
there
are
2
groups
of
sensilla,
A,
and
A,0
and
a
number
of
microtrichia,
whilst
in
A.
domesticus
there
is
an
additional
group,
A,.
The
A3
group
in
G.
bimaculatus
is
arranged
in
2
rows
of
12
14
sensilla,
with
each
row
being
composed
of
a
more
or
less
single
line
of
type
8
and
approximately
twice
as
many
type
9
sensilla
randomly
distributed
in
each
row.
In
A.
domesticus
the
A,
group
consists
of
type
8
sensilla
only
and
these
are
arranged
in
2
rows
of
6
7
sensilla
on
each
side
of
the
midline.
The
A,
group,
which
is
distal
to
the
A3,
consists
of
a
cluster
of
10
—12
type
3
sensilla.
In
both
species,
the
A,
0
group
consists
of
2
large
patches
of
type
4
sensilla
(Fig.
1),
which
lie
lateral
to
the
other
groups
in
this
field,
but
inside
the
area
demarcated
by
the
sclerotized
bars.
The
stout
setae
of
the
sensilla
vary
considerably
in
length
and
are
directed
mainly
towards
the
midline.
They
are
slightly
less
numerous
in
G.
bimaculatus
than
in
A.
domesticus.
Chapman
(1966)
found
similar
hairs
in
X.
zarudnyi
extending
from
the
tormae
(X
group
of
Thomas,
1966)
but
these
were
less
dense
and
had
smaller
setae.
They
appear
to
have
a
mechanical
function
and
probably
help
to
direct
food
particles
towards
the
hypopharynx.
Between
these
type
4
sensilla
and
the
sclerotized
bar
are
finely
sculptured
microtrichia
(Fig.
6)
which
extend
from
field
I
and
interspersed
with
these
are
a
few
very
fine
cone
-shaped
hairs.
Field
III.
This
field
includes
the
area
lateral
and
distal
to
the
sclerotized
bar
and,
in
both
species,
has
several
distinct
and
similar
groups
of
sensilla.
Group
A,
consists
of
a
small
cluster
of
type
10
sensilla
(Fig.
1),
distal
to
the
end
of
the
sclerotized
bar
(Fig.
5).
Each
cluster
has
an
approximately
equal
number
of
sensilla
and
this
is
similar
in
both
species
and
in
both
sexes.
The
SEM
micrographs
show
that
in
G.
bimaculatus
the
sensilla
are
surrounded
by
plates
of
cuticle
and
so
closely
resemble
those
found
in
group
A2.
In
A.
domesticus
the
sensilla
can
be
seen
to
have
sockets
with
a
very
small
central
protuberance
that
hardly
projects
above
the
surface
of
the
cuticle,
the
socket
being
round
and
varying
in
diameter
from
5
—6
gm.
Below
group
A,
in
both
species
is
a
bunch
of
very
fine
hairs.
Distal
and
slightly
median
to
the
A,
group
in
both
species,
is
another
group,
A
6
.
This
group
is
situated
on
the
lateral
side
of
the
inverted
Y
depression.
There
are
more
sensilla
in
this
group
than
in
group
A,
and
the
number
in
the
right
and
left
group
can
vary
considerably.
The
female
generally
has
more
sensilla
in
this
group
than
the
male.
They
are
probably
type
3
sensilla
since
each
socket
is
round
with
a
very
small
slender
seta.
In
G.
bimaculatus,
most
of
the
setae
of
this
type
are
8
10
gm
long,
with
a
basal
diameter
of
4
6
gm
and
a
socket
diameter
of
8
—10
gm,
whilst
in
A.
domesticus
the
setae
are
3
8
gm
long,
with
a
basal
diameter
of
1.5
2.2
gm
and
a
socket
diameter
of
4
6
gm.
At
the
distal
end
of
the
labrum
a
group
of
A,
sensilla
is
situated
on
each
side
of
the
notch.
They
are
type
6
campaniform
sensilla
and
may
represent
the
group
A,
of
Thomas
(1966).
In
G.
bimaculatus
there
are
usually
6
9
sensilla
in
each
group,
while
in
A.
domesticus
there
are
commonly
11
in
each
group,
although
a
range
of
7
—17
has
been
recorded.
Running
along
the
outer
edge
of
the
sclerotized
bar
in
a
lateral
position
on
each
side,
from
just
below
the
tormae
to
almost
the
distal
tip,
is
an
irregular
line
of
type
3
sensilla,
92
T.
CARLINE,
K.
KUBRA,
V. K.
BROWN
and
R.
BECK
comprising
group
A
8
.
In
both
species
the
number
in
the
group
varies
in
the
two
sexes,
the
female
consistently
having
fewer
sensilla.
In
G.
bimaculatus,
however,
the
sensilla
differ
from
those
found
on
the
anterior
surface
of
the
labrum,
they
have
the
same
shape
and
length
but
the
socket
is
more
pronounced
and
sometimes
bears
cuticular
projections
to
protect
the
seta.
Outside
the
A,
group
in
both
species
very
finely
divided
microtrichia
are
present.
Spreading
around
the
distal
margin
of
the
labrum
from
the
notch
is
the
dense
marginal
A,
,
group
of
type
4
sensilla.
In
G.
bimaculatus
most
of
the
setae
are
directed
towards
the
mid
-line,
while
in
A.
domesticus
the
outermost
setae
are
directed
outwards
and
the
slightly
smaller
inner
setae
inwards,
towards
the
mid
-line.
It
is
likely
that
they
serve
a
purely
mechanical
function.
Finally,
while
in
both
species
the
notch
itself
is
bordered
by
a
double
fringe
of
hairs
with
blunt
tips,
in
G.
bimaculatus
there
are
also
some
smaller
hairs
situated
just
behind
this
double
fringe.
The
fringe
of
hairs
presumably
serves
to
prevent
food
particles
falling
from
the
pre
-oral
cavity.
Nervous
innervation
of
the
labrum
The
labral
nerve
"Lmn",
which
is
motor
and
sensory,
originates
from
the
tritocerebrum
of
the
brain.
It
bifurcates
into
two
major
branches
"A"
and
"B",
the
bifurcation
being
more
proximal
in
G.
bimaculatus
than
in
A.
domesticus
(Figs.
9a
and
b).
The
distribution
of
the
axons
to
the
different
types
of
sensilla
and
the
shape
and
dimensions
of
the
neurones
are
presented
in
Appendix
I.
On
the
anterior
surface
towards
the
centre
of
the
labrum,
sensilla
of
types
1,
3,
7
and
13
(the
latter
only
being
present
in
A.
domesticus)
are
innervated
by
branch
"A",
while
branch
"B"
innervates
the
type
1,
2
and
3
sensilla
present
on
the
more
lateral
areas
of
the
labrum.
Each
sensillum
is
usually
innervated
by
a
single
bipolar
neurone,
although
some
type
1
sensilla
have
been
shown
to
be
innervated
by
multiterminal
neurones
(Mn).
In
G.
bimaculatus
at
least
3
multiterminal
neurones
have
been
observed,
each
with
triangular
-
shaped
cell
bodies
(5
8
gm
in
diameter)
and
3
dendrites
(9
—17
gm
in
length).
In
A.
domesticus,
2
multiterminal
neurones
have
been
identified,
again
with
triangular
-shaped
cell
bodies
(3
6
gm
in
diameter)
and
3
dendrites,
(8
16
gm
in
length).
As
can
be
seen
from
Appendix
I
the
shape
and
dimensions
of
the
rest
of
the
neurones
supplying
the
sensilla
on
the
anterior
surface
are
remarkably
similar
in
both
species.
The
posterior
surface
of
the
labrum
is
also
innervated
by
branches
"A"
and
"B"
in
both
species
(Figs.
10,
11).
Branch
"A"
passes
to
the
central
area
where
it
supplies
groups
A,
to
A6
in
both
species,
as
well
as
the
brush
border
of
the
notch
at
the
tip
of
the
labrum.
Branch
"B"
ramifies
the
periphery
of
the
labrum
to
supply
groups
A,,
A
8
,
A,0
and
All.
Only
in
the
supply
to
group
A,
is
there
any
difference
in
the
innervation
between
the
species;
in
G.
bimaculatus
the
type
8
sensilla
of
group
A,
are
supplied
by
branch
"A"
while
in
A.
domesticus,
the
sensilla
are
type
10
and
are
supplied
by
branch
"B".
However,
this
difference
is
probably
due
to
the
different
position
that
the
A9
group
occupies
on
the
labrum
in
the
2
species.
With
1
or
2
exceptions,
the
shape
and
dimensions
of
the
neurones
are
again
quite
similar
in
both
species
(Appendix
I),
but
they
are
usually
somewhat
larger
in
G.
bimaculatus
than
they
are
in
A.
domesticus.
Finally,
in
both
species,
a
number
of
stretch
receptors
are
present
towards
the
edge
of
the
posterior
surface
of
the
labrum.
These
appear
to
penetrate
the
soft
transparent
cuticle
and
may
provide
an
independent
source
of
information
on
distortion
of
the
labrum.
Comparison
of
the
Distribution
and
Nervous
Innervation
of
Sensilla
93
Lmn
A
a
t2
t
7
t
3
0.5mm
Lmn
A
b
t
2
t
t7
t3
0-
5mm
t13
Flo.
9.
Semischematic
representation
of
nervous
innervation
of
anterior
surface
of
labrum
of
(a)
G.
bimaculatus
and
(b)
A.
domesticus.
(Lmn
=
labral
nerve,
Mn
=
multi
-terminal
neurone).
Development
of
the
adult
complement
of
sensilla
in
A.
domesticus
The
number
of
nymphal
instars
in
A.
domesticus
is
known
to
vary
from
11
to
13
(Rummel,
1963;
Ragge,
1965).
The
number
of
immature
instars
in
the
culture
used
in
the
present
study
was
found
to
be
11.
Table
4
gives
the
numerical
abundance
of
each
sensilla
type
for
both
labral
surfaces
of
each
instar,
while
Table
5
summarises
the
number
of
sensilla
present
in
each
of
the
groups
(A,
A„)
on
the
posterior
surface
of
the
labrum.
Figure
12
illustrates
the
stages
of
development
of
the
sensilla
in
the
1st,
5th
and
8th
instars.
On
the
anterior
surface
of
the
labrum
of
the
1st
instar,
sensilla
of
types
1,
2
and
13
occur.
Of
the
10
type
1
sensilla,
6
are
arranged
in
2
rows
in
the
middle
of
the
labrum,
thereby
closely
resembling
the
condition
found
in
the
adult.
By
the
3rd
instar
this
type
has
attained
the
number
found
in
the
adult.
The
rudiments
of
the
4
type
13
sensilla
present
in
the
adult
are
apparent
in
the
1st
instar,
but
are
only
fully
developed
in
the
5th
instar.
Eight
type
2
sensilla
are
present
in
the
1st
and
2nd
instars
and
are
widely
scattered
in
the
area
94
T.
CARLINE,
K.
KUBRA,
V.
K.
BROWN
and
R.
BECK
a
0.5mm
Lmn
A
B
Sclerot
ised
Bar
0.5Mm
Lmn
B
Agt
4
A10t4
A11t4
b
d
Lmn
Agt8
A
A
1
t
10
A2
t
10
A
t t
Lmn
A
A5t10
A6t3
A
7
t6
FIG.
10.
Semischematic
representation
of
nervous
innervation
of
posterior
surface
of
labrum
of
G.
bimaculatus,
showing
sensilla
innervated
by
sub
-branches
"A"
and
"B".
Arrow
marks
direction
of
infusion
of
labral
nerve
with
nickel
chloride.
lateral
to
the
type
1
sensilla.
These
increase
in
number
in
the
3rd
instar
and
continue
to
do
so
until
the
adult
complement
of
24
is
reached
in
the
8th
instar.
As
the
number
increases,
this
type
of
sensillum
spreads
to
the
lateral
margins
of
the
labrum.
The
most
widespread
type
in
the
adult,
type
3,
is
absent
from
the
anterior
surface
of
the
1st
instar.
After
the
2nd
instar
the
type
3
sensilla
generally
increase
at
each
ecdysis
by
10
or
more,
although
a
far
more
striking
increase
occurs
at
the
moult
into
the
5th
instar,
where
the
number
increases
from
16
to
70,
and
also
at
the
moult
into
the
7th
instar
when
the
number
reaches
182.
A
similar
picture
is
seen
in
the
type
7
sensilla
but
the
increase
in
number
is
more
gradual.
It
is
on
the
posterior
surface
of
the
labrum
that
the
discrete
groups
of
sensilla
are
seen
in
the
adult
(Fig.
12).
Even
in
the
1st
instar
the
vestiges
of
all
11
groups
(A,
A
„)
occur.
In
most
groups,
there
is
a
gradual
increase
in
the
number
of
sensilla
throughout
development
(Table
5).
Group
A3
is
centrally
positioned
and
distal
to
the
intertorma,
and
is
the
only
group
where
the
number
of
sensilla
remains
constant.
Groups
A
4
,
A,
and
A,
have
only
a
relatively
small
number
of
sensilla
in
the
adult
and
this
is
reached
by
a
steady
increase
in
Comparison
of
the
Distribution
and
Nervous
Innervation
of
Sensilla
95
TABLE
4.
ABUNDANCE
OF
SENSILLA
TYPES
ON
THE
TWO
SURFACES
OF
THE
LABRUM
OF
ALL
INSTARS
IN
A.
domesticus
Instar
1
Surface
Anterior
t,
10
t,
8
t,
t,
iF
t,
t
6
t,
t,,
t,,
4
Posterior
46
14
2
12
2
58
2
Anterior
11
8
16
8
4
Posterior
48
18
6
12
3
58
Anterior
12 12
18
12
4
Posterior
58
29
8
12
5
66
4
Anterior
12
14
24
22
4
Posterior
62
60
8
12
13
70
Anterior
12
21
70
27
4
Posterior
63
73
8
12
17
74
6
Anterior
12
21
86
38
4
Posterior
66
129
12
12
17
78
7
Anterior
12
23
182
45
4
Posterior
66
132
13
12
18
88
8
Anterior
12
24
185
48
4
Posterior
72
178
17
12
24
112
9
Anterior
12
24
281
63
4
Posterior
80
181
17
13
24
118
10
Anterior
12
24
314
78
4
Posterior
94
194
18
13
24
132
I I
Anterior
12
24
447
85
4
Posterior
106
194
19
13
24
142
Values
are
means
expressed
to
the
nearest
whole
number.
Number
of
specimens
given
in
Table
5.
TABLE
5.
NUMBER
Ot
-
SENSILLA
IN
GROUPS
ON
THE
POSTERIOR
SURFACE
OF
THE
LABRUM
OF
ALL
INSTARS
OF
A.
domesticus
Instar
Number
of
specimens
A,
A, A, A,
Groups
of
sensilla
A,
A
6
A,
A
6
A,
A,
0
A„
1
5
18
1
6
3
4
14
1
6
7
3
4
2
2
18
2
6
3
4
14
4
9
8
4
5
3
2
18
3
6
3
4
14
4
10
10
9
5
4
2
19
6
6
4
5
14
4
20
12
28
5
5
7
19
9
6
4
6
14
4
9
11
31
6
6
3
20
9
6
4
6
14
6
27
13
44
20
7
4
22
9
6
5
8
14
6
26
14
45
21
8
2
32
11
7 7
8
14
10
58
16
54
32
9
2
33
13
7
7
9
20
9
60
17
57
33
10
3
39
14
6
7
9
26
9
72
16
61
37
11
2
46
13
7
8
10
30
10
66
17
60
38
Values
are
means
for
right
side
expressed
to
nearest
whole
number.
each
instar,
although
a
more
marked
increase
in
the
number
of
sensilla
in
group
A,
occurs
at
the
moults
into
the
2nd
and
8th
instars.
A
more
dramatic
increase
occurs
in
group
A„
and
to
a
lesser
extent
in
group
A,,
at
the
moult
to
the
8th
instar.
Group
A
6
is
composed
of
96
T.
CARLINE,
K.
KUBRA,
V.
K.
BROWN
and
R.
BECK
a
Lmn
0.5mm
A
B
Sclerotised
Bar
0.5mm
Lmn
A
B
A10t4
A11t4
d
Agtio
Lmn
A1t10
A2t10
A
B
A
3
t
8
A4t3
A
8
t
4
Lmn
A
I
t
4
A5t10
A6t3
A
7
t
6
FIG.
11.
Semischematic
representation
of
nervous
innervation
of
posterior
surface
of
labrum
of
A.
domesticus,
showing
sensilla
innervated
by
sub
-branches
"A"
and
"B".
Arrow
marks
direction
of
infusion
of
labral
nerve
with
nickel
chloride.
a
fairly
consistent
number
of
sensilla
up
to
the
9th
instar
when
an
increase
occurs.
Group
A,
is
represented
by
a
single
sensillum
in
the
1st
instar
and
it
is
not
until
the
4th
instar
that
any
marked
increase
occurs.
The
number
of
sensilla
in
group
A,
0
increases
rapidly
in
the
early
instars,
while
in
group
A,
,
the
greatest
increases
occur
at
the
moults
to
the
6th
and
8th
instars.
The
posterior
surface
of
the
labrum
is
devoid
of
sensilla
of
types
1,
2
and
13
(5,
11
and
12
are
totally
absent
from
the
labrum
(Kubra,
1978)).
The
number
of
type
8
sensilla
may
remain
constant
throughout
development,
but
sometimes
an
additional
sensillum
is
added
in
the
9th
instar.
Type
3
sensilla
increase
in
number
gradually
from
the
1st
to
the
last
instar,
while
type
4
sensilla
increase
in
number
more
erratically,
the
greatest
increases
occurring
in
4th,
6th
and
8th
instars.
Type
6
sensilla
are
present
in
group
A,
only
and
their
development
has
already
been
described.
Type
10
sensilla
display
a
steady
increase
in
number
throughout
postembryonic
development.
The
number
of
type
9
sensilla
slowly
increases
from
the
1st
to
the
9th
instar
after
which
no
further
increase
occurs.
Comparison
of
the
Distribution
and
Nervous
Innervation
of
Sensilla
97
ANTERIOR
POSTERIOR
t13
/
7
7
r
r
7
ti
t2
t13
A
l
t
10
A10t4
A8t
3
A11t4
A
9 t
10
A
2
t1
0
A
3
t
8
A4t3
A
5
tit)
A
6
t
3
A7t6
0.1mm
0.1mm
0
5
MM
/
.
'
I '
r'
'
1'
t2
t7
t3
t13
t
3
ti
t2
t
7
0.5MM
A1t10
A
8
t3
A10t4
All
t
4
Alt10
A2t10
A
8
t3
A
10t4
A
11t4
A
7
t
6
A
9
t
10
A2t10
A3t8
A4t3
A
6
t
0
A6t3
A7t6
0.5mm
A9
t10
A3t8
A
4
t3
A6t10
A
6
t3
0.5mm
FIG.
12.
Development
of
adult
complement
of
sensilla
on
both
surfaces
of
labrum
in
3
nymphal
instars
of
A.
domesticus.
(a)
First
instar,
(b)
fifth
instar,
(c)
eighth
instar.
It
is
interesting
to
note
that
the
different
types
of
sensilla
display
a
range
of
developmental
patterns,
some
not
increasing
in
number
at
all
(e.g.
type
13)
others
increase
steadily
(types
2,
6,
7,
8
and
10)
and
others
with
more
abrupt
changes
in
the
number
of
sensilla
(types
3
and
4).
Comparison
with
other
insects
The
sensilla. According
to
Slifer
(1970)
the
classification
of
sensilla
may
be
based
on
the
thickness
of
the
sensillum
cuticle.
In
this
study
however,
a
scheme
based
on
the
shape
of
the
sensillum
has
been
used.
A
similar
scheme
was
adopted
by
Thomas
(1966)
and
Kubra
(1978).
Articulated
sensory
hairs,
known
as
trichoid
sensilla,
are
excited
by
the
mechanical
deformation
of
some
part
of
the
receptor
(Dethier,
1963;
McIver,
1975).
Types
1,
2
and
4
sensilla
in
G.
bimaculatus
and
A.
domesticus
are
mechanoreceptors
and
are
innervated
by
a
single
neurone.
Type
3
sensilla
probably
play
a
role
in
mechanoreception
and
the
98
T.
CARLINE,
K.
KUBRA,
V.
K.
BROWN
and
R.
BECK
number
of
neurones
innervating
these
sensilla
varies
from
1
3
depending
upon
their
position.
Trichoid
sensilla
of
type
2
are
sometimes
grouped
together
to
form
hair
plates.
Similar
hairs
are
found
at
certain
joints
in
cockroaches
and
these
have
a
slow
rate
of
adaptation,
according
to
Pringle
(1938).
In
S.
gregaria
Thomas
(1966)
describes
the
type
2
and
3
sensilla
as
sensory
pegs
and
Slifer
(1956)
found
them
on
almost
all
parts
of
the
body
that
came
into
contact
with
the
external
environment.
Sensilla
of
type
1
appear
to
have
one
neurone
and
seem
to
be
the
same
as
the
"Type
III"
of
Blaney
and
Chapman
(1969b)
and
of
Cook
(1977).
It
is
possible
that
in
G.
bimaculatus
and
A.
domesticus
some
of
the
long
setae
of
type
1
present
on
the
labrum
may
respond
to
vibrations
of
the
substrate.
In
these
species,
as
in
other
insects
studied,
it
is
evident
that
setae
are
innervated
by
a
single
neurone.
These
hairs
may
bear
cuticular
sculpturings
such
as
grooves
or
spicules,
while
the
sockets
sometimes
bear
inwardly
projecting
ribs
or
diaphragms.
Bernays
et
al.
(1976)
also
report
the
presence
of
longitudinally
grooved
trichoid
sensilla
on
the
outer
dorsal
surfaces
of
the
1st
instar
nymph
of
S.
gregaria.
The
campaniform
sensilla
are
referred
to
as
type
6
in
G.
bimaculatus
and
A.
domesticus
and
are
innervated
by
a
single
neurone.
The
shape
of
such
sensilla
has
been
described
by
a
number
of
authors
as
semi
-spherical
(Ismail,
1962;
Schneider
and
Kaissling,
1957),
and
these
authors
suggest
their
function
to
be
proprioception.
McIver
(1975)
describes
similar
sensilla
in
other
arthropods
and
again
suggests
a
proprioceptive
function
for
them.
Their
position
in
the
2
gryllid
species
studied
here
would
also
support
this
view.
Of
the
chemoreceptors,
type
7
are
probably
olfactory
in
function.
They
appear
as
thin,
oval
or
elliptical
plates
of
cuticle
and
are
present
mostly
on
the
anterior
surface
of
the
labrum.
There
are
a
variety
of
contact
chemoreceptors,
e.g.
sensilla
trichoidea,
basiconica
and
coeloconica.
Typically,
insect
contact
receptors
possess
4
or
5
neurones,
although
6
have
been
reported
by
Blaney
and
Chapman
(1969a)
in
S.
gregaria.
Trichoid
sensilla
of
type
3,
present
in
G.
bimaculatus
and
A.
domesticus,
are
likely
to
serve,
at
least
in
part,
as
gustatory
sensilla.
However,
it
has
been
reported
in
many
insects
that
sensilla
of
type
3
may
have
an
olfactory
function
(Jefferson
et
al.,
1970).
Le
Berre
et
al.
(1967)
recognized
two
types
in
this
situation,
one
with
a
blunt
end
and
an
opening
and
the
other
with
a
pointed
end
and
no
pore.
The
latter
type
may
serve
as
mechanoreceptors.
In
G.
bimaculatus
and
A.
domesticus
the
sensilla
basiconica
are
represented
by
type
9,
present
on
the
posterior
surface
of
the
labrum.
These
are
comparable
to
the
sensilla
basiconica
of
Dethier
(1955),
which
respond
to
various
chemical
stimuli.
Dethier
has
shown
that
the
intensity
of
the
response
varies
according
to
the
nature
of
the
chemical
stimuli.
The
importance
of
these
sensilla
in
feeding
has
been
demonstrated
in
lepidopteran
larvae
by
Schoonhoven
(1969).
Type
13
sensilla
of
A.
domesticus
are
comparable
to
the
sensilla
ampullacea
or
sensory
fl
asks
reported
by
a
number
of
authors
(Barbier,
1961;
Rogciszewska
and
Fudalewicz-
Niemczyk,
1974;
Urvoy
et
al.,
1978).
They
are
innervated
by
a
single
neurone
and
it
may
be
suggested
that
they
act
as
mechanoreceptors.
Boo
and
McIver
(1975)
found
sensilla
ampullacea
on
the
antennae
of
Aedes
stephensi
and
Aedes
aegypti
(L.),
these
have
an
elliptical
-shaped
chamber.
However,
these
are
innervated
by
3
neurones
and
are
thought
to
have
a
role
in
thermoreception.
Nervous
innervation.
This
is
a
seriously
underworked
area
and
there
are
therefore
few
comparisons
to
be
made
with
other
insects.
It
is
encouraging
that
the
general
organisation
Comparison
of
the
Distribution
and
Nervous
Innervation
of
Sensilla
99
of
the
nervous
supply
to
the
labrum
of
final
instar
A.
domesticus
illustrated
by
Urvoy
et
al.
(1978)
bears
a
close
relationship
to
the
more
detailed
description
of
the
adult
given
here.
The
only
other
reports
on
the
innervation
of
the
labrum
in
Orthoptera
are
those
on
Locusta
migratoria
(Mordue,
1975)
and
Schistocerca
gregaria
(Louveaux,
1972),
although
detail
is
lacking
in
the
former.
In
both
of
these
insects
each
labral
nerve
bifurcates
above
the
tormae,
one
branch
passing
laterally
and
the
other
medially.
Each
branch
supplies
nerves
to
both
the
anterior
and
the
posterior
faces
of
the
labrum.
In
this
study
it
was
shown
that
in
Gryllus
bimaculatus
the
median
branch
of
the
labral
nerve,
"A",
supplies
nerves
to
the
median,
long
and
short
hairs
(t
1
,
t
2
and
t,)
and
the
pores
(t,)
on
the
anterior
surface.
This
branch
supplies
nerves
to
the
same
sensilla
in
A.
domesticus
but
also
to
the
ampullae
(t,
3
).
A
similar
distribution
is
seen
in
Locusta
migratoria
(Louveaux,
1972).
The
lateral
branch
also
supplies
nerves
to
types
1
and
2
and
to
the
pores
(t,)
in
A.
domesticus
and
L.
migratoria,
but
only
to
the
type
2
and
type
7
sensilla
in
G.
bimaculatus.
Mordue
(1975),
makes
no
reference
to
the
distribution
of
nerves
to
the
anterior
surface
of
the
labrum
in
L.
migratoria.
On
the
posterior
surface
in
A.
domesticus
groups
A,
A
6
are
supplied
by
nerves
from
the
median
branch
"A",
of
the
labral
nerve
and
groups
A,
A
l
by
the
lateral
branch
"B".
A
similar
distribution
is
seen
in
G.
bimaculatus
except
that
group
A
9
is
supplied
by
branch
"A"
and
not
branch
"B".
In
Locusta
migratoria
(Louveaux,
1972),
areas
corresponding
to
A,,
A
2
,
A
5
and
A
6
are
supplied
by
the
median
branch
"A"
of
the
labral
nerve
and
A,
and
A
9
by
the
lateral
branch
"B".
As
appears
to
be
supplied
by
both
branches
while
A,
and
A,
areas
have
no
corresponding
groups
in
L.
migratoria.
In
S.
gregaria
(Mordue,
1975)
only
the
innervation
to
areas
A,
and
A
2
is
stated
with
certainty
and
this
is
by
the
median
branch
"A".
Other
authors
have
looked
at
the
innervation
of
the
labrum
in
other
insect
orders:
Albert
(1980)
in
a
lepidopteran,
Choristoneura
fumiferara;
Barbier
(1961)
in
a
trichopteran,
Limnophilus
rhombicus;
Petryszak
(1975)
in
a
dictyopteran,
Periplaneta
americana;
Quennedey
(1975)
in
an
isopteran,
Schedorhinotermes
minorputorius
and
Rokiszewska
(1981)
in
a
coleopteran,
Cassida
viridis.
All
examined
the
innervation
of
the
labrum
to
some
extent
or
other
while
investigating
the
distribution
of
the
various
types
of
sensilla.
It
is
interesting
to
note
that
only
in
the
minor
soldier
castes
of
the
termite
S.
minorputorius
is
the
innervation
markedly
different
from
the
other
insects
studied.
Here
the
main
purpose
of
the
labrum
is
to
act
as
a
weapon
of
chemical
defence,
while
in
all
other
cases
it
seems
that
the
labrum
and
its
sensilla
are
mainly
concerned
with
the
reception
of
different
chemical
stimuli.
Development
of
the
adult
complement
of
sensilla.
Apart
from
studies
of
single
immature
instars
(e.g.
Urvoy
et
al.,
1978),
to
the
authors
knowledge
there
are
no
comparable
studies
in
which
the
quantitative
development
of
sensilla
types
is
followed
throughout
development.
Obviously
this
is
an
area
for
further
investigation.
Particularly
rewarding
may
be
the
confirmation
of
the
"allometric"
trends
in
the
numbers
of
certain
sensilla
types.
One
might
speculate
that
sudden,
abrupt
changes
may
be
associated
with
dietary
or
behavioural
events
during
nymphal
development.
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APPENDIX
I
Nervous
innervation
of
the
sensilla
of
the
labrum
in
G.
bimaculatus
and
A.
domesticus
TABLE
A.
1.
ANTERIOR
SURFACE
Group
Sensilla
Species
Innervation
Cell
body
shape
Cell
body
diam.
(4m)
Dendrite
shape
Dendrite
length
(4m)
Type
1
G.
bimaculatus
A,
B
Round
7
10
Straight
8
11
A.
domesticus
A,
B
Round
6
8
Straight
7
10
Type
2
G.
bimaculatus
B
Round
6
9
Straight
8
10
A.
domesticus
B
Round
6—
8
Straight
6—
9
Type
3
G.
bimaculatus
A,
B
Round
7
9
Straight
7
9
A.
domesticus
A,
B
Round
6
8
Straight
6
8
Type
7
G.
bimaculatus
A
Round
6—
9
Straight
9—
11
A.
domesticus
A
Oblong
4
6
Straight
5
11
Type
13
A.
domesticus
A
Round
5—
8
Straight
6—
9
T.
CARLINE,
K.
KUBRA,
V.
K.
BROWN
and
R.
BECK
TABLE
A.
2.
POSTERIOR
SURFACE
Group
Sensilla
Species
Innervation
Cell
body
shape
Cell
body
diam.
(pm)
Dendrite
shape
Dendrite
length
(tm)
A,
Type
10
G.
bimaculatus
A
Round
7
10
Straight
4
7
A.
domesticus
A
Round
4—
6
Curved
3—
5
A,
Type
10
G.
bimaculatus
A
Round
8
10
Straight
4
8
A.
domesticus
A
Round
4—
6
Curved
3—
6
A,
Type
8
G.
bimaculatus
A
Oval
5
8
Wavy
7
9
Type
9
G.
bimaculatus
A
Round
6—
8
Straight
6—
9
Type
8
A.
domesticus
A
Round
3—
7
Straight
3—
5
A,
Type
3
A.
domesticus
A
Round
3—
5
Straight
4—
6
A,
Type
10
G.
bimaculatus
A
Round/oblong
8
10
Straight
4
8
A.
domesticus
A
Round
3—
6
Straight
4—
6
A,
Type
3
G.
bimaculatus
A
Round
6
8
Wavy
6
8
A.
domesticus
A
Round
5—
6
Straight
3—
5
A,
Type
6
G.
bimaculatus
B
Round
4
6
Straight
4
7
A.
domesticus
B
Round
4—
6
Straight
3—
6
A,
Type
3
G.
bimaculatus
B
Round
5
7
Straight
6
8
A.
domesticus
B
Round
4—
6
Straight
5—
7
A,
Type
8
G.
bimaculatus
A
Oval
5
8
Wavy
6
9
Type
10
A.
domesticus
B
Round/oblong
4
6
Curved
or
wavy
3
5
A,
o
Type
4
G.
bimaculatus
B
Round
5—
7
Curved
6—
9
A.
domesticus
B
Round
3—
5
Curved
4—
7
A,
,
Type
4
G.
bimaculatus
B
Round
5
7
Curved
6
9
A.
domesticus
B
Round
3—
5
Curved
4—
7
Comparison
of
the
Distribution
and
Nervous
Innervation
of
Sensilla