408 Wisconsin Academy of Sciences, Arts, and Letters. 
The larvae of Palpomyia longipennis and Probezzia pallida 
resemble each other in form, but differ greatly in size; both are 
white, and have a vibratile method of locomotion,—like that 
of a rod which is fastened at one end and permitted to vibrate 
freely at the other. Probezzia glaber is pale green, and ex¬ 
tremely attenuated; it swims in regular, worm-like undula¬ 
tions. 
For emergence the pupa of P. longipennis climbs up the sides 
of rocks and rubbish, while the other two species emerge from 
the water surface. Parallel to this is the ability of the Prb- 
bezzia species to rest on the surface-film and oviposit through it, 
while Palpomyia breaks thru the film and must therefore ovi¬ 
posit from solid objects. 
These larvae have an interesting method of letisimulation. 
When grasped while in the water they straighten out and be¬ 
come rigid; this is one of the few cases where aquatic insects 
feign death in their normal environment. Since their color 
resembles that of the filamentous algae among which they live, 
the larvae may be said to be doubly protected. In spite of 
this, they are quite frequent in fish stomachs. They are quite 
resistant to digestion, specimens having been taken alive from 
perch stomachs several hours after capture of the fish. 
The Ceratopogoninae are among the free-swimming insect 
larvae although not pelagic. They do not build tubes or shel¬ 
ters such as the Tanypinae and Chironominae. Their range ap¬ 
pears to be limited by the oxygen distribution of the lake; in 
winter, like the fish, they go to deeper waters, but with the ad¬ 
vance of the thermocline they migrate toward-shore. For respi¬ 
ration they evert retractile gills from the anal opening. 
They pupate in July, and during June and early July form the 
chief Chironomid contingent of the littoral catches. Three other 
species of Ceratopogoninae have been found in Lake Mendota, 
but I have been unable to breed them; they are not abundant. 
According to the sex, the larvae show a dimorphism in size, 
the female larvae being uniformly larger than the males. 
Tanypinae. 
The habitus of the Tanypinae is more Chironomid-like. The 
larvae resemble those of the true Chironomids, while the pupae 
bear a strong resemblance to the Corethra type. In many 
