THE SYRPHIDAE OF OHIO \^ 



Aphidophagous species deposit their eggs on various parts of plants 

 which are, or will generally be, infested with plant-lice. Eristahs tcnax 

 was found depositing eggs on or near the surface of very foul water. 

 The former species deposit their eggs singly, gluing them flat to the 

 surface especially by the posterior end; those of Eristalis sp. were found 

 in masses, the eggs ranked side by side and nearly perpendicular. (Fig. 

 142.) Wheeler believes that adults of Microdon frequently oviposit in the 

 same nest in which they mature, VerhoefT observed adults apparently 

 trying to oviposit among the ants on the outside of the nests. 



I have noted no methods of natural protection except the sheltered 

 position in which they are sometimes placed; nor have I found any egg 

 parasites. 



GENERAL CHARACTERS: THE LARVA 



The larvae of Syrphidac which I have had an opportunity to exam- 

 ine represent four distinct larval habits, and, structurally^ are of at least 

 three quite different kinds. 



These all agree in belonging to the eruciform type of larva. They 

 are slug-like, legless, with the segmentation not well marked and the 

 head not differentiated. They are of medium size, commonly about one 

 centimeter long, sometimes considerably larger. They have no eyes and the 

 antennae are very rudimentary. The mouth and anus are terminal or 

 slightly ventrad at the two extremities. The esophagus has a more or 

 less complex frame- work of chitinized parts extended to, or modified into, 

 mouth-parts. 



Typically the larvae bear anterior and posterior spiracles. I have 

 not been able to locate anterior spiracles on the specimens of Microdon 

 which I have examined. However, the anterior spiracles are often incon- 

 spicous in the other forms and, while they may be wanting here I sus- 

 pect they may yet be found upon examination of more and better mater- 

 ial. Buckton states that he was never able to trace a tracheal connection 

 to the opening of the anterior respirator)^ cornua in the larvae ol Eristalis. 

 I am convinced that these spiracles are functional. Comparatively large 

 tracheae run to them and are open to the tip; if a larva is submerged and 

 compressed bubbles of gas may be seen to form in connection with the 

 teeth-like lobes. There is no doubt that the similar structures in aphi- 

 dophagous larvae are also functional. 



In one type of larva which is exemplified esi^ecially by the aphi- 

 dophagous species we have the tough- skinned, terrestrial larva with well- 

 developed, beak-like, chitinous jaws and mouth-hooklets adapted for 

 catching and eating their prey. In this type the anterior spiracles are 



