June, 1912.] Life-Histories of Syrphidae IV. 535 



The skin is finely papillose when magnified. The character 

 of the visceral matter often gives the larva a very granular appear- 

 ance. The segments are marked by the usual twelve bristles in a 

 transverse row. These are light in color, not elongate and not at 

 all consi^icuous ; and are the only vestiture present. 



The character of the mouth-parts is more or less perfectly 

 represented by Figure 67. Owing to the lack of favorable material 

 I was unable to verify this drawing and it may not be perfectly 

 accurate. The outer pair of mouth-hooks is present. 



The caudal branchial appendage is prominent, elongate, about 

 0.5 mm. in length by 0.125 mm. in breadth; of two cylinders fused 

 mesad except at the extreme tip where they diverge slightly( Figs. 

 66, c; 68). The usual three elongate spiracles and circular plate 

 are present on each half. The spiracular elevation is about three 

 times as long as broad. There is a short, spur-like spiracular 

 spine between each two spiracles, one between the most dorsal 

 spiracle and the plate, and one mesad from the most ventral 

 spiracle. These spines are continued down the sides of the tube 

 as more or less evident ridges. 



Larvae of this species were fotmd abundant on the leaves of 

 flowers and fruit of the persimmon {Diospyros virginiana L.) on the 

 University Campus June 1 and 2*. They were feeding on the 

 nymphs of an undetermined species of Aleyrodidce which caused a 

 curling of the leaves. 



An autumn generation occurs commonly on cabbage and related 

 plants w^here they are predaceous on Aphis hrassicce. Larvae were 

 taken from this host-plant at the University Farm from September 

 20 to October 10. 



Near Lakeville in Wayne Co., larvae were taken from curled 

 dock, June 16-18; and at Sandusky, Ohio, from the same plant 

 June 23. These were among colonies of Aphis riimiciis. 



The larvae are thus seen not to be closely restricted in their 

 food habits, attacking at least two species of Aphid idee and one of 

 Aleyrodidce. 



These larvfe live entirely on the surface of the plants where they 

 are found and probably do not move farther than is necessary to 

 secure their food. On the persimmon the larvae were found on the 

 flowers, but chiefly on the leaves, especially under the rolled up 

 edges, where the Aleyrodid nymphs were commonest. On Rumex 

 they were to be found mostly in the spikelets and on the under side 

 of the leaves where the plant lice occur. 



Whatever the host, the method of feeding is the same. The 

 body-wall of the aphid is pierced by the mouth parts and the soft 

 contents picked and sucked out while the head is pushed farther 

 and farther inside the victim's skin. 



*I am indebted to my fellow-student, Mr. J. Lyonel King, for first 

 calling my attention to these specimens. 



