326 
The Two-winged Flies 
ish or blacK and red, strong legs, large clear or smoky wings, and stout an¬ 
tennas about as long as head and thorax together and composed of nine to 
twelve segments. They may be seen often in large numbers flying heavily t 
over gardens and fields or in woods, early in the spring. The eggs are laid 
in the soil or in decaying vegetation or in sewers and excrement, the larvae 
feeding usually on decomposing substances. With some species, however, 
the larvae feed on the roots of grains or grasses and in this way may do serious 
damage. Bibio tristis , discovered in Kansas in 1891, appeared in great 
numbers in wheat-fields and frightened many wheat-growers. As a matter 
of fact, little injury seemed to be done. B. jemorata , a common species,, 
is deep red with black wings; B. albipennis , another abundant and wide¬ 
spread one, is black-bodied with white wings. A common Californian species 
appears from the ground in damp woods in great numbers in March. I 
have watched these flies issuing in countless numbers 
from the soft rich forest floor in the extensive 
Monterey pine woods near the Bay of Monterey 
Fig. 454. 
Fig. 454. —March-fly, Bibio albipennis. (Three times natural size.) 
Fig. 455. —Diagram of wing of Bibio albipennis , showing venation. 
The air danced with them, and the pine-trees and shrubs bore countless 
myriads on their branches. Professor Needham records a similar sight 
in which individuals of B. jraternus formed the hosts, and a woodland pasture 
near Lake Michigan was the scene of their appearance. “I have rarely 
come upon a scene of greater animation than a sheltered hollow in this wood 
presented,” writes Professor Needham. “There was the undulating field 
clad in waving grass and set about with the pale-hued 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 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 counted a number 
of flies I could see resting on the grass in several small areas wide apart, and 
