THE CANADIAN ENTOMOLOGIST 87 



leaves when held up to the light arc so mined that the characteristic larva is 

 readily identified as a Brachys sp., while others have the mined area so brown 

 that the light will not penetrate. However, a Brachys sp. mine can usually be 

 identified as such by the dried, oval, flat, glistening egg shell which remains 

 sticking to some portion of the upper surface of the mine long after the larva 

 has left it. Mined leaves were found on small as well as large trees. On the 

 large trees, however, only the outer leaves exposed to plenty of sunlight were 

 infested. 



Not all of the trees selected as food plants by theadu Its seem to harbour 

 the larvae in their foliage, and we have observed mines of both species only, 

 as a rule, in the leaves of various oaks. In a few cases we have noted mines on 

 chestnut and have taken larvae therefrom. At Uhlerstown, Pa., eggs and adults 

 of B. aerosus were plentiful on red maple leaves, but an opportunity for visiting 

 this place later in the season was not afforded us, and it is not known if the 

 leaves were mined. 



In general, the life-history of both species is as follows. Adults appear 

 about the middle or latter part of May and disappear by the first part of August, 

 being most plentiful during June and the first part of July. Soon after emergence 

 and feeding, eggs are deposited on the upper leaf surfaces, many being laid near 

 the edges. After hatching, the larvae mine the leaves until the latter part of 

 August and September, at which time many leave the mines through the lower 

 surface and drop to the soil where pupation takes place. Sometimes it is possible 

 to find larvae in their mines as late as the middle of October. The winter is 

 evidently passed in the pupal stage, as a specimen under our observation pupated 

 during the first part of October. 



Egg of B. ovatns. Length 2.2 mm. Width 1.7 mm. Flat, oval, rounded 

 at both ends. Side resting against leaf flat. Upper surface slightly convex. 

 Chorion apparently smooth, shining. Transparent when first laid, later be- 

 coming yellowish white. Just before hatching larva can be seen through the 

 transparent chorion, resting with the abdomen bent back sidewise upon itself 

 the tip touching the second thoracic segment. Except for its smaller size, 

 (Length L7 mm., width LI mm.,) the egg of B. aerosus appears to be similar 

 to that of ovatus. 



In depositing the egg, the female protrudes the tip of the vagina slightly 

 and rubs it back and forth against the leaf surface. This operation which ends 

 in three or four minutes results in an oval, flat, transparent, watery-like mass, 

 the outer surface of which soon hardens into a thin film or skin. The entire 

 thing resembles an oval drop of transparent, watery excrement rather than an 

 egg. 



Of a pair of B. ovatns collected May 27 and placed in a cage, the female 

 deposited sixteen eggs. A pair of B. aerosus collected at the same time and 

 caged resulted in the female depositing forty-five eggs. Another pair of aerosus 

 yielded thirty-five eggs. Inasmuch as no eggs were noted in the field when the 

 specimens were collected, these numbers may be fairly representative. All of 

 the above specimens lived and fed for six weeks, the eggs being deposited during 

 the first four. All eggs were deposited on the upper leaf surface, many of them 

 close to the edges. As a rule, leaves uninjured by adult feeding were selected. 

 The young lar\'a usually enters the leaf tissue directly beneath the egg and mines 



