4 CONNf:CTICIT OEOL. AND NAT. HIST. SURVEY [Bull. 



The number of esTfrs produced per female is often fairly larg-e, 

 but there is some correlation with the life cycle and habits. The 

 crane-fly, Eriocera longicornis. lays about 950 eggs, and the house 

 mosquito lays 100 to 400. The tachinid Whifhemm qv^dripustulata^ 

 which oviposits on caterpillars, probably lays between 50 and 60 

 eggs at most, whereas Sturmia scuteUata, which deposits its eggs on 

 leaves where they are swallowed by feeding caterpillars, lays about 

 5,000. The common housefly lays its eggs in batches, and one female 

 may deposit between 2,000 and 3,000 during its life. Pupiparous 

 flies, in contrast to the above, have few progeny per female. The 

 female sheep tick deposits 10 or 12 fully grown larvae singly at inter- 

 vals of 7 or 8 daj^s. 



The eggs or larvae are as a rule deiDosited on or near the larval 

 food supply. Thus blow-flies oviposit on carrion, houseflies in a 

 manure heap, mosquitoes on the surface of pools or in depressions 

 which will later be flooded, black-flies on rocks in flowing streams, 

 and fruit flies in f!"uit. The females of s])ecies parasitic on other 

 animals commonly lay their eggs on the body surface of the host. 

 Most tachinids place their eggs on the integument of host insects, 

 but some, as mentioned above, lay their eggs on leaves where leaf- 

 feeding caterpillars can swallow them, and others deposit larvae 

 inside caterj^illars by slitting tlie integument with a larvipositor. 

 Female Avarble flies lay their eggs on the hairs of the host, and horse- 

 bots have a like habit. Predaceous species lay their eggs in the region 

 where the prey of the larvae, occur. Horse-fly larvae are predaceous 

 on small invertebrate animals whicli they find in wet earth or in the 

 water. The eggs are laid on vegetation or stones close to the larval 

 habitat. 



'i'he ]:)eriod of incubation of most fly eggs is relatively short, 

 although it may depend entirely on en vironmentaL conditions. Where 

 the larval food supply is temporary, or the survival of the larva is 

 otherwise endangered by a delay in hatching, a short incubation 

 ])eriod is essential. High temperatures accelerate the incubation of 

 eggs, and low temperatures prolong it. Dryness inhibits the hatching 

 of the eggs of many species, but the larvae emerge quickly if moisture 

 is supplied. The housefly egg hatches in 8 to 12 hours at 77° F. to 

 95° F., and in 2 or 3 days at 50° F. Blow-fly (Calliphora) eggs hatch 

 in 6 to 48 hours. The minute eggs of leaf -ovipositing tachinids hatch 

 within a very short time after getting into the intestines of caterpillars. 

 The eggs of the apple maggot, which are laid in the fruit, have an 

 incubation period of 5 to 10 days. Some species of mosquitoes have 

 a long period of incubation of the eggs mider certain conditions. 

 Aedes stimulans deposits its eggs in dry woodland depressions in the j 

 summer, and these hatch when the areas are flooded the following I 

 spring. The eggs of Aedes soUicltans are deposited on the surface of * 

 a salt marsh where a pool has dried. Submergence with water after 

 a few days in summer causes them to hatch, but it is said that hatch- 

 ing may not occur for three years if the marsh remains dry during 

 the intervening summers. The eggs of sj^ecies of Psorophora^ a fresh- 



