INSECTS INJURIOUS TO CEREALS 



265 



screens. They are also abundant in decaying fruit in 

 apple orchards and their larvae are sometimes mistaken 

 for those of the apple maggot, Rhagoletis pomonella. 



It should be said that not all of the species of the genus 

 Drosophila live in fruit. Some of the species mine in the 

 leaves of plants, especially cabbages and radishes. These 

 species have been separated from the genus by some au- 

 thorities and placed in the genus Scaptomyza. Most 

 authors, however, recognize this only as a subgenus. 



Fig. 84. — A fruit-fly (D. ampelophila) . (X 10.) 



Probably the most common species of fruit-flies in this 

 country are D. ampelophila (Fig. 84) and D. amama. 

 These are about one-eighth of an inch in length, but their 

 wings are rather large proportionately. Their bodies are 

 reddish-brown in color and clothed with rather stiff hairs. 



The tiny, white, elongated egg is deposited by the female 

 in the soft pulp of the decaying fruit. During the month 

 of October Comstock found the duration of the egg stage 

 to be from three to five days. 



The larva is a slender white maggot about J of an inch 

 in length. It takes from three to five days for it to mature. 

 When full-grown it changes to a brownish pupa (Fig. 85) 



