52 OHIO BIOLOGICAL SURVEY 



Again, parasitized puparia may be destroyed before the parasite has 

 had a chance to emerge. The characteristics b}" which these infested 

 puparia may be recognized (see above) are such that they should be 

 clear to anyone with a little experience. 



Other methods of favoring these insects in general farm-practise as, 

 for example, by av^oiding them in spraying for aphids, etc., will suggest 

 themselves to ever}' agriculturist. 



Part II. 



KEY TO THE KNOWN LARVAE AND PUPAE OF SYRPHIDAE 



1. Body terminating in a long, flexible, rat-tail-like appendage (often longer than the 



body), at the tip of which the posterior spiracles are located. (PI. VII, 



Figs. 131-133); larvae aquatic or semi-aquatic 2 



Posterior breathing appendage considerably shorter than one-fourth the length 

 of the body, rigid, larvae terrestrial 4 



2. Anterior respiratory cornua of the larva has the spiracle guarded by 7-9 elon- 



gate teeth (PI. VI, Figs, iii, 112, 113). Pupal respiratory cornua 

 about twice as long as broad, its tubercles with 3 or 4 nodules on their 



tips (PI. VI, Figs. 1 1 lb, 114, 115) Chalcomyia aerea 



Anterior respiratory cornua of the larva has the spiracle guarded by about 20 

 blunt, rounded teeth (PI. VII, Figs. 131a, 132). Pupal respiratory cornua 

 four or five times as long as broad, its tubercles with 7-9 nodules on their 

 tips. (PI. VII, Figs. 145b, 147, 148) 3 



3. Mature larva about 20 mm. (four-fifths inch) long, excju.sive of the "rat- 



tail" Eristalis tenax 



Main body of mature larva 13-15 mm. (slightly over one-half inch) long. (PI. 

 VII, Fig. 131 ) Eristalis aeneus 



4. Larvae short-oval or rounded in outline, the shape constant; convex above 



and with a very flat, creeping-sole ventrally, around which is a special- 

 ized marginal fringe of spines; the dorsum often nicely reticulated. (PI. 



IX, Fig. 182) Microdon spp. 



Larvae elongate-oval when at rest, much attenuated toward the anterior end 

 when active 5 



5. Larvae phytophagous; most dorsal of the three pairs of spiracles on posterior 



respiratory appendage rounded. (PI. IX, Figs. i93-i94)Mesogramina polita 



Larvae aphidophagous; most dorsal of the three pairs of spiracles on posterior 



respiratory appendage elongate, slit-like 6 



6. Length of posterior breathing tubes at least two or three times their combined 



width, see also Paragus tibialis. Larvae and pupae deep green in color 

 with two prominent, white, longitudinal stripes on the dorsum; integu- 



mental spines wanting 7 



Posterior breathing tubes shorter, or but little longer, than their combined 

 width, never twice as long; colors yellowish or reddish-brown 8 



7. Tip of posterior breathing appendage roughened, the spiracles well-elevated 



above the general surface and separated by spur-like elevations. The tubes 

 very slightly divergent at the tip. (PI. V, Figs. 66-68) Allograpta obliqua 



