86

N. Chari et al.

10.

High-frequency flapping wing sheds the vortex at the tip of the wings. These

wing tip vortices accumulate one on the above as a cushion and press against

the next flapping stroke during hovering.

11.

Cicada is an ideal reference for hovering flight in insects because of its large

weight to wing size ratio. Cicada is a fast flier.

12.

Wingspan remains more or less constant during hovering.

13.

Usually, the hovering frequency is high, and the variation in frequency range

depends upon whether the insect is a neurogenic or myogenic flier.

14.

The neurogenic nature of flier is not influenced by wing tip mutilations.

However, in myogenic flier after wing tip mutilations, the frequency increases

considerably.

15.

Basically, the soapnut bug is a myogenic flier that has become neurogenic

because of adaptation to the sedentary way of life on soapnut trees during the

prolonged course of evolution.

Differences between Symmetrical and Asymmetrical Hovering (modified after

Chari 2014).

S.No

Symmetrical Hovering

Asymmetrical Hovering

1

Common in Hummingbirds and some

insects

Seen in Kestrels and Kingfishes

2

Body mass 2–30gm, flight position is

vertical

Body mass is relatively high, flight

position is horizontal

3

Wings move forward and backward and

rotate at the base

Wings move up and down and do not

rotate at the base

4

Differential lift is produced during each

stroke

Most lift is produced during downstroke

and upstroke is recovery stroke

5

Wings rotate at the fulcrum during

pronation and supination

Wings do not rotate at the fulcrum

6

Hovering is due to wingbeat frequency and

forward velocity is zero

Hovering is assisted by incoming wind also

7

Figure of ‘8’ is vertical in plane

Figure of ‘8’ is horizontal in plane

8

The wing is relatively rigid and chambered

at the wing tip

During the upstroke, the wing, flexes and

primary feather open up

9

In hovering insects, the lift produced may

be 50% or more. In hummingbirds, the

downstroke produces 70% lift

The lift produced during downstroke may

be about 90% and the upstroke is a

recovery stroke

10

Hovering frequency ranges from 10–80cps

The hovering frequency is low and is about

10–15cps