196 



INSECT CALENDAR. 



month, is the Rose Saw fly (Selandria rosae, Fig. 236) and S. 



cerasi. The eggs are then laid, and the last of June, or early in 

 July, the slug-like larva? mature, and 

 the perfect insects fly in July. Various 

 Gall flies now lay their eggs in the 

 buds, leaves and stems of various kinds 

 of oaks, blackberries, blueberries and 

 other plants. 



Dipterous Gall flies are now laying 

 their eggs in cereals. The Hessian 

 fly (Cecidomyia destructor) has two 

 broods, the fly appearing both in 

 spring and autumn. The fly lays 

 twenty or thirty eggs in a crease in 

 the leaf of the young plant. In about 

 four days, in warm weather, they 

 hatch, and the pale-red larvae "crawl 

 down the leaf, work- 

 ing their way in be- 

 tween it and the main 

 stalk, passing down- 

 ward till they come 

 to a joint, just above 

 which they remain, a 

 little below the sur- 

 face of the ground, 

 with the head tow- 

 ards the root of the 



plant. Here they imbibe the sap by suction 



alone, and, by the simple pressure of their 



bodies become imbedded in the side of the 



stem. Two or three larvae thus imbedded 



serve to weaken the plant and cause it to wither 



arid die. The second brood of larvae remains 



through the winter in the flax-seed, or pupa- 



rium. By turning the stubble with the plough 



in the autumn and early spring, its imago may 



be destroyed, and thus its ravages may be 



checked. (Figure 237 represents the female, 



which is about one-third as large as a mosquito: a, the larva; 



&, the pupa ; and c represents the joint near the ground where 



235. Water Flea. 



Selandria rosae. 



