THE SVRPHIDAE OF OHIO 3^ 



II. Larvae living within, and dciivino their food from— 



(A) "The stems of plants such as Sonchns, Scrophularia, 

 Rlatricaria; genus Chilosia;'' 



(B) /;/ r(?r//.- genus I'olncella; 



(C) /// bulbs, as of Narcissus and Amaryllus: genus Merodon; or of onion: 



genus Eumerus; 



(D) In fungi {as Boletus edulis):^Qn^ra Chilosia, Platychirus. 



Species which could feed successfully in this manner, especially those in fungi 

 lead very naturally to the third group. This group cannot be strictly separated froui 

 the succeeding one and the two might be combined. But the two lists of genera 

 exemplifying these habits, as divided, are very distinct; and further this third group 

 makes a very perfect and illuminating step in this line of evolution of larval habits. 



III. Larvae living — 



(A) In decaying wood or trees, some of them ^'rat-taitedr' genera, Malloia 



Sptlomyia, Xylota, Brachypalpus, Pocota, Myiolepta, Chrysotoxum; or 



(B) In sap flowing from injured or diseased trees: genersi, Brachyopa, Cht'vso- 



chlamys, Xylota, Ceria, Chrysotoxum, Myiolepta.^ 



(C) Bred from larvae found under bark of oak: genus Crioprora (by Osten 



Sacken); o/ cotton-tree: genus Xanthogramma (in Riley's collection). 

 This habit is almost continuous with the fourth. 



IV. Larvae living in decaying vegetable ur animal matter; in heaps of turf in 



soft mud containing vegetable matter; in manure or foul excrement- even 

 reported to have been passed from the human alimentary canal; in putrid 

 stagnant ivater; or even in zvaternig troughs, luells, etc., ivherethe ivater is 

 not conspicuously contaminated: genera, Platychirus, Eristalis, Helophilus 

 Crwrhtna, Syritta, Orthoneura, Chrysogaster, Xanthogramma, Sericomyia 

 RJnngta. ' 



It is possible that this group might be considered as derived from its aquatic mem- 

 bers, thru a stage in which they lived within the stems of aquatic plants- but the line 

 of evolution suggested above is the more probable since it leads gradually to the 

 aquatic forms which are most specialized structurally. 



The question arises whether this group is a unit, structurally. Some of the mem- 

 bers are certainly "rat-tailed." But, according to Williston, Platychi rushes this habit 

 and the larvae of Platychirus spp. are structurally of the same form as the aphido- 

 phagous species. 



Groups II to IV clearly represent one, more or less continous line of evolution 

 from the primitive phytophagous habit. Another line of specialization from the 

 same original habitat is shown by those members of the group which have taken up 

 the predaceous habit. 



V. (A) Larvae predaceous on soft-bodied insects living in colonies, especially 

 plant-lice (Aphididae); but also feeding on nymphs of/assidae, Aleyrodi- 

 dae and Membracidae; on adults of Musca domestica and Chortophila 

 pusilla; and even on larvae of other species of Syrphidae: genera, 

 Baccha, Sphaerophoria, Pipiza, Paragus, Didea, Allograpta, Melano- 

 stoma, Syrphus and Catabomba . Paragus and .lllograpta are, I believe, 

 added to this list for the first time, by the present studies. (See Part 

 II.PP-53. 54, S-'^O 

 Syr p. 4 



