223 



succeed in emerging. This is almost invariably tlie case when the 

 hinder part of the body of one individual overlaps the fore-part of the 

 body of another. The skin of the latter may then sjdit, but the adult 

 is unable to lift the body of the other sufficiently to issue unharmed. 

 When the insect is ready to emerge from the pupa shell, the skin splits 

 along the median line from near the front edge of the head to the front 

 edge of the abdomen, and thjence transversely to the hiteral margin, as 

 indicated in Fig. 23 i. The thorax of the adult insect is then pushed 

 out hrst, and afterwards, gradually and slowly, the head. After the 

 head has been extruded the insect remains stationary in an upright 

 position. The legs seem to be free at this stage, but are not withdrawn 

 from the pupa shell. The wings are rolled up as indicated in the figure 

 just referred to, and make their appearance with extreme slowness, the 

 legs remaining within the shell apparently to give a purchase which 

 assists in this extrusion of the wings. Just before the adult is ready 

 to issue from the pupa shell the latter becomes transparent, so that the 

 contained insect, shrunken away from the skin, is plainly seen in all 

 of its details, as shown at Fig. 23 h. In this stage the insect looks like 

 the pupa of a Psyllid. 



The color of the adult just after issuing differs somewhat from that 

 of the more mature individuals. The thoracic lobes are bright lemon- 

 yellow and highly polished, the head and prothorax are milk white, the 

 antennae pale yellow, eyes reddish brown, ocelli colorless, lower lobe of 

 eyes purple. The wings at first appear i^erfectly colorless and trans- 

 parent with the costa pale yellowish, the powdery whiteness so char- 

 acteristic of these flies gradually appearing. 



The eggs seem to be laid by preference upon the new leaves in April 

 and May, although old leaves are also frequently well covered. The 

 eggs remain usually about two weeks at this time of the year before 

 hat(;hing, although some remain unhatched for three weeks or a little 

 longer. The egg splits along the margin at the end farthest from the 

 pedicel and extending for some distance down the sides, so that when 

 the young larva issues the eggshell resembles to a slight extent a bi- 

 valve shell, especially that of a freshwater clam. 



The young larva is comparatively active, and crawls usually a short 

 distance from the shell before beginning to feed. It remains in the first 

 stage from two to four weeks before molting. The cast skins are very 

 delicate and usually drop to the ground or are blown away by the Avind, 

 so that very few of them remain attached to the leaf. The exact periods 

 between the succeeding molts have not been satisfactorily ascertained, 

 but by June 14 a majority of the individuals have cast three skins. 



In preparing for a molt the insect curves the abdomen upwards at 

 considerably more than a right angle, moving it also occasionally up 

 and down. The margin of the abdomen has at the same time a slightly 

 undulating motion. During these movements the insect is shrinking 

 away from the lateral margin until it eventually occupies only about 

 one-third of the original lateral space, causing a distinct dorsal and 



