40 OHIO BIOLOGICAL SURVEY 



It seems liekly that the usual and preferable food of these species is Aphids, and 

 that these other cases are largely exceptional and due to the absence of their accus- 

 tomed food. 



An interesting specialization of this habit, which so far as I know, has not been 

 previously reported, in which the aphidophagous larvae live, not on the exposed sur- 

 face of the host-plant but enclosed in galls, makes a sub-division of this group. 



V. (B) Larvae predaceous on the gall-inaking ap/iids, Pe>nphigiis ami Colopha 

 a>id living cvithin their galls; Syrphus xanthostovius and another 

 species, at the time of this writing undetermined. 



When I had studied these larvae for a little time and noted their sluggishness I 

 was struck with the probability that they were on the road to degeneration and possibly 

 to true parasitism. In view of this conviction it was with much satisfaction that I 

 noted the report of larval habits which I embrace in the third sub-division of this 

 group. 



V. (C) Larvae said to have been bred fi out pupae of species of Plusia (Ento. 



Month. Mag. XXXIV, 244.): Lasiophthicus (Scaeva, Catabomba) 

 pyrastri. 



If this report be authentic the larval habits of Syrphidae will take on additional 

 interest as presenting a most instructive and perfect series, leading from free-living, 

 phytophagous forms thru facultative and obligate predatism on individuals (or 

 parasitism on the colony) to a condition of true internal parasitism on the individual. 

 Aldrich (Catalog N. A. Diptera, p. 363) considers this an error and states that he has 

 reared the species from larvae feeding on the grain aphis, Siphonophora avenae. 

 The original article by E. N. Bloomfield is as follows "Last Autumn I received from a 

 friend, a cripple specimen of Cataboinba pyrastri, L. which he had bred from a pupa 

 of Plusia iota; and this summer he sent me from Southwold, several larvae (most 

 probably Plusia gamma), asking if I could tell him what they were. Two or three 

 at once spun up, and became pupae, and to my surprise in about a fortnight two 

 specimens of C. pyrastri were disclosed; the empty pupae cases giving indubitable 

 proofs that they had proceeded from them." 



I have a puparium of this species from California from which it can be seen that 

 the larva is essentially similar to aphidophagous larvae. 



VI. Larvae living in the nest of colonial insects, chiefly Hyinenoptera: 



(A) Of the large Aculeate Hyinenoptera (Bombus, I'espa): genus Volucella. 

 These larvae were formerly reported as parasitic on the immature Hymenoptera 



but it now seems certain that their relation is rather that of scavengers. (See pp. 37- 

 38) (Verrall makes a second division here of those larvae living in the nests of small- 

 er Aculeate Hymenoptera. He states that he has no evidence to support this group 

 but strongly suspects Eumerus and Paragus. As the present studies have shown that 

 this suspicion is unfounded so far as /^aro^//^ is concerned the group may be omitted, 

 pending definite evidence.) 



(B) Of ants (Formica, etc.) primarily, but also of termites and zvasps; genus 

 Microdon . 



Adlerz believed that the larvae of M. mutabilis feed on the moist pine 

 wood thru which the galleries run. Wheeler, however, found that the young larvae 

 shrivel and die when removed from the ants; which may indicate that their food 

 supply is inseparably connected with the ants. Wheeler, indeed, believed "that it is 

 the minute pellets of food, which after their moisture has been extracted, are ejected 

 from the hypopharyngeal pockets of the worker ants. These pellets are scattered 



