#insect flight

cicadas are powerful, fast fliers, and all of their thorax is taken up by a bulk of reddish, stringy flight muscles, which I’ll talk more about later. this cicada is a female, so her abdomen is full of white, elongated eggs that she will insert into tree bark with the bladed ovipositor at her rear.

the male cicada’s abdomen, however, is almost entirely empty, and that air-filled space is used as a resonator for his loud calls. the biggest structure visible there is a curved pair of muscles that deforms the tymbals, producing a click with every contraction.

here's a view of the complete muscle, and the tymbals themselves which look like overlapping plates on his belly. if you're curious what the white frosted appearance is, some Neotibicen have a coat of waxy powder or pruinescence; this male N. tibicen is particularly pruinose.

onto the flight muscles:

powered flight is a pretty complex mechanism in any organism, and is never so simple as just flapping wings up and down, but most insects power their flight in a really unintuitive way (at least for us vertebrates): they contract muscles in their thorax that aren’t even attached to the wings!

this method of flight is called indirect flight, in contrast to the direct flight of the dragonflies and mayflies where each of four wings is directly attached to a muscle and can flap on its own.

instead, most insects have a longitudinal (image 1 above, d below) pair and a vertical (2, c) pair of muscles that deform the shape of abdomen, pulling the upper segment of the thorax (notum) up and down, and this moves the wings which are attached to the notum. useful indirect flight gif from wikipedia found here

even if compressed manually, the dead cicadas "flap" their wings due to the motion of the notum:

More insect flight magic from Dr. Adrian Smith at Ant Lab.

Insect flight in glorious slow motion!

The North Carolina Museum of Natural Science’s ANT Lab, as part of the Evolutionay Biology & Behaviour Research Lab, has made a spectacular video about insect flight. It’s filmed in juicy slow motion and features orthopteran, coleopterans, dipterans, a hemipteran, and even some psocoptera which are little proto-hemipteran like critters.

The full species, in order of appearance:

nut/acorn weevil (Curculio sp.)

broad-nosed weevil (Asiatic oak weevil Cyrtepistomus castaneus)

Hook-faced Conehead katydid (Pyrgocorypha uncinata)

bush katydid (Scuddderia sp.)

Lesser Angle-wing (Microcentrum retinerve)

Mouse-like Barklouse (Lichenomima sp.)

common barklouse 1 (subfamily: Psocinae)

common barklouse 2 (subfamily: Psocinae)

common barklouse (Cerastipsocus venosus)

March fly (Penthetria heteropteran)

however, the bit that actually bothers me is perpetrating that myth about insect flight (”According to all known laws of aviation, there is no way that a bee should be able to fly. Its wings are too small to get its fat little body off the ground.”). It’s not true! The ‘known laws of aviation’ have been able to account for insect flight for like half a century at least.

I guess an introduction along the lines of

The overly simplified quasi-steady state aerofoil-based model first developed in 1918 after high-speed video of flying insects first became available was unable to account for two thirds of the lift in insect flight, but improved experimental work in 1956 (moving in a wind tunnel) and 1973 (hovering) found with better data, the quasi-steady-state model model accounts for the bee’s lift within error.

This does not mean that model is an accurate description, and more recent computational and experimental work on insect flight from 1979 onwards has observed discrepancies from the quasi-steady-state model due to dynamic effects, such as the leading edge vortex which prevents the wing from stalling despite its high angle of attack and increases lift; see Wang (2005) for a recent review of work on insect flight.