Insect wing, Modifications and Copulation
INSECT WING, ITS
REGIONS, VENATION AND MODIFICATIONS
v
Insects
have a pair of wings in thorax.
v
Wings
are located dorso-laterally between the nota and pleura of the meso- and meta-thoracic
segments.
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The
wing bearing segments (meso- & metathorax) are called pterothorax.
Wing venation
The
arrangement of veins in the insect wing is called wing venation. Each
wing consists of a thin membrane supported by a system of thickened tubular
veins. The membranous area between the veins is called cell. The veins
strengthen the wings and give rigidity besides aiding blood circulation. Insect
wing consists of longitudinal (principal)
veins, which runs along the length,
and cross veins, which connects the
longitudinal veins.
A
hypothetical wing will have the veins as follows:
|
Longitudinal
veins/ principal veins
|
Cross
veins
|
|
|
Regions
Insect
wings can be differentiated into many regions. The distal portion of the wing
supported by veins is called remigium, while the proximal portion at the base is axillary region / axilla. Below the remigium and in proximity with
the basal region are two flexible regions called vannus and jugam.
Remigium and vannal lobe or anal lobe is separated by anal or vannal fold,
while jugal fold separates vannal lobe and jugal lobe.
Margins
The
anterior margin of insect wings is called coastal margin, the posterior margin
beyond remigium is the apical margin, while the jugal and vannal margin
constitute the anal margin.
Modifications
of insect wings
|
Modification
|
Description
|
Example
|
|
Tegmina
|
Thick
and leathery
|
Forewing
of cockroach, grasshopper
|
|
Elytra
|
Sclerotized
and horny
|
Forewings
of beetles
|
|
Hemelytra
|
Basal
half thick and distal half membranous
|
Forewings
of plant bugs
|
|
Halteres
|
Knob
like, at the base sensory cells (Hick’s papillae) & scapal plates present
|
Hindwings
of house fly, forewings of stylopids
|
|
Fringed
|
Bristle
like, feathery
|
Thrips
|
Pterostigma: Dragonflies and damselflies have a
dark rectangular spot along the coastal margin of the fore and hind wings
called stigma / pterostigma.
Scales: The wings of butterflies and moths
are covered by tile like structure called scales, in an overlapping
arrangement. These wing scales are responsible for the bright, attractive,
multi-varied coloration in butterflies and moths.
Wing
coupling
In
insects, both the fore and hind pairs of wings are closely associated or linked
as a single unit, to achieve an efficient flight. This is called wing coupling.
Types of wing coupling
a)
Amplexiform: The broad fore and hind wings are
basely overlapping each other. Eg. Swallow tail butterfly
b)
Frenate: large bristles (frenula) of the hind
wings interlock with downwardly curved hook (retinaculam) of the forewing. Eg.
Fruit sucking moth.
c)
Jugate: A long and finger like structure
(fibula) arising from the jugal lobe of forewings lies on the coastal margin of
the hind wing during flight. Eg. Few primitive lepidopterans
d)
Hamulate:
A row of curved small hooks (incurving hooklets) called the Hamuli is
present along the coastal margin of the hind wing that interlocks with the
thickened anal margin of the forewing. Eg. Honey bees.
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