84 - The Ohio NatunilisL [Vol. XIII, No. 5, 



Eristalis aeneas Scopoli. 



(Plate V, Figs. 131 to 141 and 14.5 to 148; and Plate IV, 



Figs. 149, 150.) 



The egg of Eristalis (rneas was not found but that of its near 

 relative E. tenax was studied and is figured in Plate V, 

 Fig. 142. 



These eggs are much larger than those of most of the aphid- 

 iphagous species studied, but are equaled in size by the egg of 

 Didea fasciata. Length 1.6 mm., diameter 0.4 mm., elongate 

 ovoid, slightly bent, rounded at the ends, the anti-micropylar end 

 the larger. The shell shows the usual sculpturing but the radi- 

 ating arms between the main bodies are much less conspicuous or 

 at times apparently wanting (Fig. 143). There are about 65 

 bodies the length of the egg, about 100 around it at the middle. 

 Each body is about two or three times as long as broad, with 9-13 

 short arms radiating from it. The bodies are well separated from 

 each other. The color is the usual chalk-white. 



A female of E. tenax was taken at the city sewage disposal 

 plant while ovipositing over filth, September 23. Within an 

 hour and a half after being taken she had deposited about 100 

 eggs. Part of these were deposited in more or less scattered 

 positions; the great majority, however, in one or two masses, in 

 which they were ranked on end, their sides closely apposed. They 

 were floated over a vial of water, and within 24 hours a consid- 

 erable number of them had hatched and were to be seen crawling on 

 the vial or wriggling in the water. 



Larva. 



The young larva of E. tenax (Fig. 144) is scarcely longer than 

 the egg except for the projection of the posterior respiratory 

 appendage. Including this structure the length, 2 or 3 hours after 

 hatching, was 2.5 to 3 mm. The larvae are sub-cylindrical 

 but attenuated at the posterior end to the breathing tube (Fig. 

 144, d). They frequently show a prominent hump dorsally in the 

 posterior third of the body. Antennae (a), prolegs {b), tracheal 

 trunks (c), and other larval structures are ]3resent but these are 

 described below for the larva of E. ceneas. 



The mature larva of Eristalis ceneas (Fig. 131) resembles in a 

 general way the well-known rat-tailed larva of E. tenax, but is 

 considerably smaller. 



The body is .soft, slug-like, elongate-oval or sub-cylindrical in 

 shape, about 13 to 15 mm. long by 3 to 4 mm. l)n>a(l and 2 to 3 

 mm. high; these dimensions varying with the different positions 

 assumed by the motile larva. The anterior end is commonly 



