ig2 



THE AMERICAN ENTOMOLOGIST. 



was so great as to grind to pieces the 

 mature forms when they came free, so it 

 was with great difficulty I secured three 

 specimens for identification. 



I doubt if their eggs have ever been 

 seen before. " The eggs of the Simulia or 

 Sand-fiy appear to be at present unknown; 

 there is, however, little doubt that, like 

 those of other gnats, they are deposited on 

 the surface of the water, and in that situ- 

 ation are hatched by the warmth of the 

 sun, combined with the moisture of the 

 water." {Newman, Hist, of Insects.) 



[Fig. 103.] 



Eggs uf Simulium: apportion of mass from side; /', do. 

 from top J c, d^ single eggs — enlarged (after Barnard). 



The eggs are long-ovoid in form, measur- 

 ing 0.40 X 0.18""". They are united in a 

 compact layer, often with the sides so 

 pressed together as to make the form some- 

 what polyhedral, and generally with one 

 end a little flattened or concave. When 

 the fresh egg has imbibed glycerine, a 

 large, somewhat irregular spheroid nucleus, 

 with its distinct spherical nucleolus, ap- 

 pears at one end. The embryonic devel- 

 opment proceeds as usual with other flies. 

 The young larva is larger at the anal end, 

 which is the last to be withdrawn from 

 the egg-membrane. Its terminal aperture 

 serves as a sucker to attach by, and has its 

 thick margin covered by rows of minute 

 elevated points. Adjacent to this, the 

 youngest larva bears some transparent 

 cylindriform appendages, at least three 

 in number, which are soon to disappear. 

 In front of the anal segment is a ventral 

 prominence. Its convex surface can be 

 retracted to form a concavity or vacuum 



which helps the larva to cling fast and is 

 essentially a quasi-sucking-disk. The pro- 

 thorax bears a single proleg, nearly as long 

 as the head, with its distal end covered by a 

 great number of minute denticles or hook- 

 lets. This and the anal area are the two 

 points on which the maggot walks, somewhat 

 as loopers or measuring-worms do, only, by 

 doubling itself sidewise, it brings one end by 

 the side of the other,which is then advanced 

 again. Two slender antennje, each appar- 

 ently with two segments, and later three, 

 are noticed on the sides of the head. 

 Above the somewhat hairy lower lip is a 

 pair of mouth-appendages, which may re- 

 present palpi, each with many short hairs 

 on its end and side. Still higher are the 

 maxillee and a pair of remarkable mouth- 

 parts, which would naturally represent a pair 

 of mandibles. These are short arms, each 

 bearing on its end an incomplete whorl of 

 extremely long, slender, curved, radiating 

 hooks or bristles, forming rake-like or 

 comb-like appendages, which keep up a 

 grasping, raking motion toward the mouth, 

 seemingly to capture and rake out from 

 the water and into the mouth floating or- 

 ganisms as food. This end of the body is 

 generally elevated somewhat in the water, 

 while the anal end is usually adherent. 

 The larvffi, although light at first, soon 

 become black except on the ventral sur- 

 face. They grow about 1.50™ long before 

 transforming. A viscid secretion draws 

 out into strong silk fibre. It is strange 

 how this substance can harden in water 

 without drying. The larva when loosened 

 from its hold will hang in the swift current, 

 anchored by its thread, or when lifted 

 from the water, several may hang together 

 pendant on these telegraph lines, which 

 seem also to connect the individuals with 

 each other, for they are on a kind of web- 

 work. Finally the full-grown larva spins 

 on the surface of the rock a net-like silken ! 

 cocoon, which is boot-shaped, open above | 

 and inclined down-stream at an angle with I 

 the horizon. In this the pupa form is 

 taken on, its thorax filling the aperture 1 

 above and bearing some long prongs which j 

 project out from it. These queer append- ! 



