‘entomon' and `logos'; ‘entomon’



Download 8.6 Mb.
Page29/36
Date conversion15.05.2018
Size8.6 Mb.
1   ...   25   26   27   28   29   30   31   32   ...   36

Flight of Insects:


Insects are the only invertebrates that can fly.Insect flight can be extremely fast, maneuverable and versatile. This flight is possible due to the changing shape, extraordinary control and variable motion of the insect wing. Insect orders use different flight mechanisms, for example, the flight of a butterfly can be explained using steady-state, non-transitory aerodynamics and thin aerofoil theory. 


Insect Wings Venations:


Insect wings have rigid veins which support the wing in flight. The wing veins may look different in different insect groups, scientists tracked that all different insect wings are evolved from the same ancestor, i.e. wings had evolved only once in the insects history. In most cases, a characteristic network of veins runs throughout the wing tissue.  These veins are extensions of the body's circulatory system.  They are filled with hemolymph and contain a tracheal tube and a nerve.  In membranous wings, the veins provide strength and reinforcement during flight.  Wing shape, texture, and venation are quite distinctive among the insect taxa and therefore highly useful as aides for identification.

 

Typical insect wing venation (modified Comstock-Needham System)

 

In the insect history, the fossil records show that the early insect wing had 8 pairs of main veins. Each pair diverged from wing base intoanterior convex and posterior concave sector (e.g. MA and MP). The two sectors often fused into one veinal stem near the wing base. In evolution insect wing is in most case modified in reduction of veins.



 

Precoasta (PC) -- This vein is fused with costa in all extant insects, mostly unrecognisable. 

Costa (C) -- at the leading edge of the wing, strong and marginal, extends to the apex of the wing, it is unbranched.

Subcosta (Sc) -- the second longitudinal vein, mainly the subcosta posterior sector (ScP)Sc is reduced or fused with R in most Hemiptera.

Radius (R) -- the third vein, usually the strongest vein on the wing, with branches usually cover the largest area of wing apex. RP is often referred to as radial sector (Rs) and the end branches as R1-5.

Media (M) -- the fourth longitudinal vein, MA and MP usually with 4 branches each. In some insect groups MA fused with R so onlyMP on the medial area. In this case the MP1-4 are often referred as M1-4.

Cubitus (Cu) -- fifth longitudinal vein, CuA may branch to 4 or fewer veins. CuP is unbranched, lies near the claval fold and reach the wing posterior margin.

Anal veins (A) -- veins behind the cubitus, AA and AP are usually separated by the anal fold. In Neoptera, AA is always fused with Cuor CuP. In the hind wings of most orthopteroid insects, there is a large anal area where anals branch several times to form a fan-like folded wing.

Jugal (J) -- small veins in the jugal area, found only in Neoptera.

 

The black pterostigma is carried near the wing tip, between RA1+2 and RA3+4.



 

Cross-veins are transverse veins joining longitudinal veins. Their names are based on the position relative to longitudinal veins, e.g. r-m is the cross-vein between radius and media.








Characteristic
Wing adapations and modifications:


Appearance

Order(s)

Elytra -- hard, sclerotized front wings that serve as protective covers for membranous hind wings



Coleoptera 
and 
Dermaptera

Hemelytra -- front wings that are leathery or parchment-like at the base and membranous near the tip



Hemiptera: Heteroptera

Tegmina -- front wings that are completely leathery or parchment-like in texture



Orthoptera,
Blattodea,
and Mantodea

Halteres -- small, club-like hind wings that serve as gyroscopic stabilizers during flight



Diptera

Fringed wings -- slender front and hind wings with long fringes of hair



Thysanoptera

Hairy wings -- front and hind wings clothed with setae



Trichoptera

Scaly wings -- front and hind wings covered with flattened setae (scales)



Lepidoptera

Hamuli -- tiny hooks on hind wing that hold front and hind wings together



Hymenoptera

Frenulum -- Bristle near base of hind wing that holds front and hind wings together



Lepidoptera


1   ...   25   26   27   28   29   30   31   32   ...   36


The database is protected by copyright ©dentisty.org 2016
send message

    Main page