62 OHIO BIOLOGICAL SURVEY 



GENERIC REVIEW OF BIOEOGY 



Microdon — Earvae and pupae of this genus have been described as 

 two or three different species of Molluses as well as listed among the 

 Coccidae. The}' have been discovered in the nests of a dozen species of 

 ants and of I ^espa crabro in Europe as well as in the nests of termites in 

 Madagascar and Brazil. In North America Microdon tristis seems to be 

 the only species which has been reared from the larval stage. According 

 to Wheeler, the species referred to as M. globosus by Packard and Eint- 

 ner is M. tristis. This species has been taken in the U. S. with Formica 

 schaiifussi , F. rufa obscuripes, F. difficilis var. consociaiis, and F. sanguinea 

 aserva. Larvae of at least three other undetermined species have been 

 described. (See W. M. Wheeler, "Ants," pp. 383-386; Psyche, July, 

 1901; and Journal N. Y. Ent. Soc. Vol. 16, pp. 202-210, 1908. Also 

 Sharp. Camb. Nat. Hist. Vol. VI, Part II, pp. 501-502.) 



Chrysotoxum — "The metamorphoses are believed to take place in 

 rotten wood, or in the diseased sap of trees, btit very little is known about 

 them." — A^errall, British Flies, p. 642. 



Chrysogaster — "The larvae of two European species have been bred 

 from the mud of a ditch." — Verrall, p. 186. 



Pipiza — Riiey in his P'irst Mo. Rept. 121, fig. 66, and in Amer. Entom. 

 I, 83, describes Pipiza femoraUs Eoew. , under the name of ' 'The Root-louse 

 Syrphus Fl}- (Pipiza radicum n. sp.)," as an enemj' of the apple-root 

 Plant-louse (Sc/iizoncura lajiigera) and in his 6th Mo. Rept. asanenemj' 

 of the Grape Phylloxera {Phylloxoa vastatrix Planchon). I quote from 

 these papers as follows: 



This "footless maggot" is about one-half an inch long, and of a dirty yellow 

 color. It is generally found more or less covered with mud, and with the wooly 

 matter secreted by the lice, and is not by any means easily discerned. It changes in 

 the fall to the pupa state from which, in the following spring, there emerges the 

 perfect fly. 



'■'■Larva — Dull pale flesh-color, tinged with yellow. Attenuated and somewhat 

 depressed anteriorly, more blunt posteriorly, the anal segment being furnished with 

 an elevated tube which is of a light polished brown at extremity. Wrinkled trans- 

 versely, with a prominent fold at anterior and posterior edge of each segment. The 

 larger segments well defined; the smaller ones less so. First segment thoroughly 

 retractile and sufficientl}^ translucent when extended to show the dark triple-jointed 

 mouth. A few soft, fleshy spines of the same color as the body especiallj- distinct 

 on anal segments. Length when not extended 0.23 of an inch. From five speci- 

 mens." 



"Pupa — Dull dirty yellow. Gradually formed by the contraction of the larva, 

 (luring which time the wrinkles are obliterated, at last becoming quite smooth. 

 Length 0.18 inch." A puparium buried in moist sand twice crawled up the side of 

 the bottle in which it was contained. 



