90 The Ohio Naturalist. [Vol. XIII, No. 5, 



Didea fasciata Macquart, var. fuscipes Loew. 

 (Plate IV, Fig. 17.) 

 (An addition to the life-history notes on this species published 

 in The Ohio Naturalist, Vol. XI, No. 7, pp. 337-341, May, 1911). 



Elongate oval in outline, sub-cylindrical, but flattened ven- 

 trally and arched slightly dorsally; broadest about the middle. 

 Length 1.3 to 1.7 mm., diameter 0.4 to 0.6 mm. Color chalk 

 white. The chorion is sculptured in a characteristic manner. 

 The projecting bodies are close together, not highly elevated, 

 each one two to four times as long as broad. There are oo to 60 

 of these bodies lengthwise of the egg and SO to 100 around it at 

 the middle. The egg of Didea differs from all the others I have 

 seen in that the projecting bodies are not smooth on the top but 

 each one has a small number (6-10) of more or less angular, 

 irregular-shaped, pit-like depressions hollowed out of it. These 

 are so arranged as to leave between them an elevated part of the 

 body with more or less parallel sides. The whole effect is to give 

 the arm-like network appearance over the main body somewhat 

 like that between these bodies, without the outlines of the bodies 

 being obscured. The arms between these bodies are irregular, 

 slightly branched, for the most part rather short, sometimes 

 long, from 10 to 15 radiating from each body. 



Eggs already hatched and larvte apparently 5 or 6 days old 

 were taken on sycamores at Columbus, September 28, 1911. A 

 number of eggs, not hatched, and nearly full-grown larvas were 

 taken October 7. 



The eggs are scattered singly along the under side of the low, 

 spreading, more or less horizontal branches of the sycamore 

 {Platanus occidentalis L.) at a time in autumn when the colonies 

 of aphids {Longistigma caryte Harris) are just being established, 

 or even in anticipation of their arrival. Indeed it seems to me 

 likely that the latter is usuall}^ the case. Certainly many eggs 

 can be found in branches where no aphids are yet to be seen. They 

 are laid flat down, glued by the posterior half of the ventral side 

 to the bark, and are of such a size and color as to be readily seen 

 on close examination with the naked eye. 



EXPLANATION OF PLATE IV. 

 Figures 81-89 Syrphus xanthostoma Wills. 



Fig. 8L Antero-ventral view of head of larva much enhirged; a, sensory 

 papillae; b, antenna; c, upper jaw; d, outer pair of mouth-hooks; 

 e, other mouth hooklets; /, lower jaw; g, anterior spiracles or 

 larval respiratory cornua; h, oesophageal framework, within. 



Fig. 82. Lateral view of larva, x 6; a, median segmental spines; b, pos- 

 terior respiratory ap])endage. 



Fig. 83. End view of anterior spiracle, highly magnified. 



Fig. 84. Dorsal view of posterior respiratory organ x 40; a, one of the 

 three pairs of slit-like spiracles; b, one of the inter-spiracular 

 spurs; c, the median dorsal spiracular spur; d, the circular plate. 



