35° 
The Two-winged Flies 
than two weeks. Thus even in the short season of the fruit ripening and 
gathering much injury can be and often is done by these little tipplers. 
A much larger group of fruit-flies is the Trypetida, whose larva burrow 
in fruits or plant-stems, often producing galls on these latter. The familiar 
spherical swelling or gall on goldenrod stems is the hiding and feeding place 
Fig. 499.—Puparia of cherry-fruit fly, Rhagoletis cingulata. 
size and much enlarged.) 
(After Slingerland; natural 
of the thick white larva of Trypeta solidaginis, a pretty fly with banded 
wings. The longer hollow gall which sometimes occurs on goldenrod 
is made by the caterpillar of a small moth, Gelechia gallce-solidaginis. 
Some Trypetid species do much injury by burrowing into fruit, as the apple- 
maggot, and the larva of a black-and-white fly with 
banded wings known as Trypeta ludens, whose 
larva infests Mexican oranges and may sometime 
get a foothold in California or Florida. 
W ^ Another group of small flies whose larva are 
responsible for serious injury to growing grain, 
meadows, and pasture grasses are the Oscinida, 
or grass-stem flies. The adults are commonly taken 
by collectors when beating or sweeping in meadows 
and pastures. The flies are minute but plump, 
and are variously colored, sometimes blackish, 
sometimes yellowish. They are so small that they 
often get into one’s eyes in their swarming-time, 
and are said to cause a prevalent disease of the 
eyes in the South. The thick cylindrical little larva of several species of 
Oscinis live in the stems of wheat, barley, oats, rye, and grass. The larva 
of Chlorops similis burrows in the leaves of sugar-beets, and another 
Fig. 500. — An aquatic 
muscid, Sepedon fasci- 
pennis , larva, pupa, and 
adult. (After Needham; 
two and one-half times 
natural size.) 
