X] LARVA 



175 



and generally possess long respiratory syphons. In addition 

 the larvse of 5. fasciata possess the following characters : 



The antennae are smooth, the tuft being represented by a 

 single short hair. At the apex there is a minute but distinct 

 second joint and a few dehcate hairs. The labial plate pos- 

 sesses one large terminal tooth and 11 or 12 smaller ones on 

 each side of it. The thorax is rather hairy and bears four 

 large chitinous hooks, two on each side. Each of these hooks 

 gives off one or two hairs. The abdomen is very broad, and 

 is almost the same width all the way down. 



The two lateral combs, situated on the eighth segment, 

 each consist of eight to ten serrated spines, varying in size 

 and the number of serrations. The syphon is comparatively 

 short and stumpy, being only one-quarter the total length 

 of the abdomen, and about two and a half times as long as its 

 width at the base. The syphon spines vary both in number 

 and arrangement ; they are succeeded by a triple hair. The 

 terminal segment of the abdomen is very short and almost 

 rectangular and bears a number of blunt bifurcate hairs. 

 The papillae are broad and rounded ; their length is about 

 one and a half times that of the last segment. 



The larvae feed on decaying organic matter, especially on 

 nitrogenous substances. They thrive best in neutral or shghtly 

 alkaline water, and soon die if free acids are present. Although 

 still capable of development in very brackish water, S. fasciata 

 cannot hve in sea-water, as at least one other species of the 

 genus (S. pseudoscutellaris) has been shewn capable of doing. 



After a number of moults the larva gives rise to the pupa. 

 The duration of the larval stage at fairly warm temperatures 

 varies from seven to fifteen days, but a temperature of below 

 20° C. will prolong development almost indefinitely. The young 

 larvje are remarkably tenacious of hfe under water and will 

 stand submersion for three to five hours. The fully grown 

 larvje can still endure a submergence of at least one and a 

 half to two hours, a property which enables them to feed at 

 the bottom of comparatively deep water. 



There is no record of the live larvae of Stegomyia ever 

 having been found in ice, as in the case of those of the alhed 



