ORDER DIPTERA 255 



The egg is milky white and flattened from above and below. 

 It is broadly rounded at each extremity and slightly con- 

 stricted at the middle. It is from 0.45 to 0.50 mm. long. 

 These are deposited under the upper or lower epidermis of 

 the leaf. They are usually placed at the tips of the leaves. 

 The feeding punctures and the egg laying punctures of the 

 female are similar. In making the puncture the fly forces 

 the point of her abdomen downward rearing the anterior 

 portion of her body slightly and touching the tip of the abdo- 

 men to the leaf, whereupon the small lancets, which appar- 

 ently make up the ovipositor are put in motion. They are 

 forced down between the two surfaces of the leaf and a 

 strip of the epidermis about 0.3 mm. in width and about 0.9 

 mm. long is pushed back. The egg is then inserted and the 

 flap is in some way brought back over the egg and fastened 

 probably with a mucilagenous substance. 



The larva mines towards the base of the leaf forming a 

 broad linear or sometimes a blotch mine. This may alter- 

 nate from the upper to the lower side of the leaf. The larva 

 cannot enter a new leaf and must mature within the leaf on 

 which the egg was laid. The larvae are gregarious, several 

 mines unite bringing the larvae in a common mine. There 

 are possibly four or five broods in this latitude. When ma- 

 ture the larvae escape and transform outside the leaf. They 

 hibernate as puparia. 



The iris leaf -miner {Agromyza later ella Zett.) . This unique 

 leaf -mining and gall-forming species has been studied in some 

 detail by Claassen (1918). We take the following account 

 from his studies. 



The flies emerge the latter part of May from their over- 

 wintering galls. The female inserts her eggs into the tissues 

 of the leaf causing rather conspicuous abrasions. When the 

 eggs hatch delicate mines are formed on the innermost 

 leaves. The mines are at first so delicate to be hardly 

 perceptible to the naked eye. The mine is linear enlarging 



