350 



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. 



.\ 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, Rlicjc;nleli': cingiilnta. {Aiter Slingerland; natural 



size and much enlarged.) 



of the thick white larv.T 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 gallcc-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 

 larvffi infests Me.xican oranges and may sometime 

 get a foothold in California or Florida. 



Another group of small flies whose larva- are 



resjionsible for serious injury to growing grain, 



meadows, and pasture gra.sses are the Oscinidae, 



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 



two and one-half times often get into one's eyes in their swamiing-time, 



and are said to cause a prevalent disease of the 



eyes in the South. The thick cylindrical little larvae of several species of 



Oscinis live in the stems of wheat, barley, oats, rye, and grass. The larva 



of Chlorops simiiis burrows in the leaves of sugar-beets, and another 



Fig. 500. — .\n aquatic 

 musrid, Sepedon fusci- 

 pennis, larva, i)upa, and 

 adult. (After Needham; 



