6

N. Chari and P. Srinivas

(12)

Apart from having low wingbeat frequency (30–40 Hz), insects like dragonfly

and mayfly possess complex mesh type of wing venation and cannot fold their

wings as in other insects.

(13)

Variations are found in the wing structure of several orders. Beetles

(Coleoptera) possess two pairs of wings, of which the first pair is hard

and leathery known as elytra. This is partially true for some Heteroptera.

In housefly (Diptera), the second pair of wings become rudimentary, acting

as halters to balance during flight and vibrate for detecting changes in direc-

tion. They are gyroscopic in their action. Halters vibrate out of phase with

the wings and they can detect very fast rotation.

(14)

Bumblebee, honey bee and wasp (Hymenoptera) have two pairs of thin

membranous wings, while thrips have small fringed wings.

(15)

Plant bugs (Heteroptera) have the first pair of partially chitinous wings and

the second pair of thin membranous wings. In Homoptera, both the wings are

similar as in cicada which make figure of ‘8’ (as in Hummingbirds).

(16)

Mostly, the first and second pair of wings on each side of the thorax get

coupled by special hooks and move as a single unit during flight.

(17)

By moving the wings up and down, insects take advantage of unsteady

mechanisms (delayed stall, rotational lift and wake capture) for their flight.

(18)

The evolution of insects and their successful flight was the result of their

low body mass, membranous wings, elastic resilin at the fulcrum, as well as

coupled with a relatively high wingbeat frequency, spiracles and tracheal

system supplying more oxygen to oxidative aerobic flight muscles, open

circulatory system and chitin as the exoskeleton.

(19)

Robotic insect fliers using Micro-Electromechanical Systems (MEMS)

designing for bio-mimicking MAVs have been suggested. However, it is rather

difficult to use in the design of bio-mimicking MAVs.

Anatomy

(1)

Insects have evolved successful flight due to a systematic arrangement of

several systems (digestive, circulatory, excretory and reproductive) which are

medially located in the body. The dorsal location of pulsating tubular heart is

a notable feature. There is no haemoglobin in the blood. The heart is typically

divided into chambers varying from 1–9. The circulatory system is open. The

ventral solid double segmental ganglionated nerve cord has been derived from

Annelid ancestry.

(2)

The blood or haemolymph consists of fluid plasma having nucleated cells and

no haemoglobin.

(3)

Some of the bio-mimicking flight characters in biological flight as mentioned

are common to insects, Micro Air Vehicles (MAVs) and Nano Air Vehicles

(NAVs). Hence, the study of the Aerodynamics of Insect Flight is essential for

a better understanding of the various parameters required in the design and