90 
The Ohio Naturalist. 
[Vol. XIII, No. 5, 
Didea fasciata Macquart, var. fuscipes Locw. 
(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). 
Egg- 
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 O.G 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 55 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 larvae 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 larva 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 carycc Harris) are just being established, 
or even in anticipation of their arrival. Indeed it seems to me 
likely that the latter is usually 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. 81. Antero-ventral view of head of larva much enlarged; 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 appendage. 
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. 
