182 Annals Entomological Society of America [Vol. XIII, 



The species of aquatic, scavenger, or parasitic habits are 

 free from the restrictions governing the development of those 

 species dependent upon living plants, but the life-cycle of the 

 gall-makers, leaf miners and fruit flies is often built around the 

 annual cycle of the host plant and we find many nice adaptations 

 for the utilization of the potentialities of the plant tissues by 

 attacking them at the exactly right time in their development. 



THE EGG. 



The egg stage shows many adaptations to its environment 

 and in anticipation of the welfare of the subsequent larva. 



The adults lack a definite ovipositor of chitinous appendages 

 yet the terminal abdominal segments may be adapted to insert 

 the eggs into the softer tissues of plants, fruits, etc., as in 

 the Trypetidas. Much more frequently the eggs are simply 

 dropped, deposited, or glued to the surface of the substratum, 

 on or in which the young may find nourishment. They may 

 be (a) laid singly, (b) arranged in indefinite, irregular blotches 

 or masses, (c) ranked with some definiteness but not fastened 

 to each other, or (d) most carefully arranged in a definite man- 

 ner with respect to each other, and fastened with a cement-like 

 secretion. The cyrtid female expels the eggs forcibly in great 

 numbers while hovering up and down a tree trunk (King*) ; 

 conopids attach them to their host while in fiight ; sarcophagids 

 will drop their young through a screen to food material some 

 distance below. The interesting manner in which the female 

 Culex holds the first few eggs upright between her crossed 

 hind legs until enough can be fastened together to make the 

 raft float has been described by Howard, et al.f Miall| 

 describes some beautiful adaptations by which the eggs of 

 aquatic Diptera are moored at the surface of the water. Chiro- 

 nomus eggs are laid in gelatinous ropes that are held in place by 

 peculiarly twisted threads. The raft of Culex eggs floats by 

 its own convexity, the single eggs of Aedes and Anopheles have 

 curiously moulded air floats to decrease their specific gravity. 

 The female ephydrid may crawl under water to fasten her eggs 

 to submerged objects. 



*King, J. L. Observations on the Life History of Pterodontia fiavipes Gray, 

 Jn Annals Ent. Soc. Amer., IX, 3. Sept., 1916, 315. 



fHoward, Dyar and Knab, The Mosquitoes of North and Central America 

 and the West Indies. 



JMiall, L. C. The Natural History of Aquatic Insects. 



