
No. 423.] . REMARKABLE OCCURRENCE (‘OF THE FLY. 183 
leaves... The flight:of the males is long sustáined;: -Both males 
and females, and especially the latter, have- some -difficulty-in 
getting launched. | They climb to a leaf top, balance carefully, 
stretch their wings and try them:before letting go, — 
swing free into the air. 
I have rarely come upon a scene of greater animation than a 
sheltered hollow in this wood presented. Theré was the tndu- 
lating field, clad in waving grass and set about with the pale- 
hued springtime foliage of the white oaks; there. were the 
flowering. hawthorns ; and there were the myriads. of. Bibios 
floating in the sunshine, streaming here and there like chaff 
before sudden gusts and swirls of air, All the spiders’ webs 

E B 
A, larva of Bibio fraternus Loew., lateral view. B, pery view of head of female 
pupa. C, ventral view of male p 
in the bushes were filled with captives ; little groups of ants 
were dragging single flies away to their nests, and once I saw 
overhead a chestnut-sided warbler, perched on a bare bough 
directly in a stream of passing flies, rapidly pecking to right 
and to left, persistently stuffing his already rotund maw, 
I stood in one spot and swept the air with my net for half a 
minute and obtained 128 male Bibios and 5 females : ratio, 25: 1. 
I swept the grass a few times with my net and thus obtained 
127 males and 372 females : ratio, 1: 2.2. The discrepancy of 
ratios is due to the fact that a comparatively small proportion of 
the flies were inthe air. I counted.a number of flies I could see 
resting on the grass in several small areas wide apart and found 
the counts averaged 15 Bibios per square foot; and there were 
here in one place forty acres of such Bibio territory! There can 
` 1 Professor Herbert Osborn notes the of Bibia albipennis in phe- 
nomenal numbers in Iowa, in Jnsect Life, vii iii (1891), p. 479. 
