THE SYRPHIDAE OF OHIO 37 



to everyone. This species in general color and size, in proportion of 



head to thorax to abdomen, in vestiture, in size and proportion of the 



wings, and distinctness of the veins, in manner of buzzing about flowers; 



in fact, in almost every respect except the length of the antennae, is a 



striking mimic of the honey bee (Apis meUifcra), especially of the drone. 



A few other of the more striking resemblances may be named: 



Temnostoma alternans to J^espa diabolica, the yellow jacket; Spiloniyia 



fusca to W'spa maculata, the bald-faced hornet; Volucella evecta and Eris- 



talis flavipes\.o Bombus spp. bumblebees; and Ceria abbreviata to Odyneriis 



philadelphiae . The list might be extended to considerable length b)^ 



a comparison of numerous specimens from the two groups. 



REPUTED AGGRESSIVE MIMICRY 

 Some of the species of the Genus Vohicella resemble, in the adult 

 stage, certain bees and wasps; and the larvae of several species are known 

 to live in the nests of the large Aculeate Hynienoptera, especially in Europe. 

 It has long been supposed that the larvae lived on the immature bees in 

 the nest and that the resemblance was of great significance in enabling the 

 parent flies to enter the nests of the bees for the purpose of oviposition 

 without being detected and antagonized. Folsom and others refer to 

 this as an instance of Aggressive Mimicry which has resulted from the 

 action of natural selection. This seems however not to be founded on 

 observed facts. The larvae live in the bees' nests, and the adults, which 

 resemble the bees, enter the nests to la}- their eggs. In doing this they 

 met with no resistance in the cases observed. Erne who watched the 

 Volj(ccl/a larvae in the nests, thought they acted as scavengers, eating the 

 waste and excrement of the larvae. Sharp, who kept some of the larvae 

 under observation, found that they .starved without eating the honey, or 

 the larvae and pupae of Bombus, which were provided for them; that 

 they did not attack the pupae of wasps in the comb; but that when a pupa 

 of the wasps was broken in two, they attacked it eagerly. 



We must therefore believe that the.se larvae live on either excrementi- 

 tious matter or on pupae which have recently died, thus preventing the 

 contamination of the ne.st; and hence that, however the resemblance of the 

 adults to the bees is to be explained, it is not now aggressive mimicry. Is 

 the theory not barely tenable, however, that the habits represented by 

 Volucella and Microdon (though not now predaceous) have been deri\-ed 

 from a true predatism by a s])ecialization in which they began to eat the 

 injured, or dead, or more or less putrified bodies of larvae and pujiae, and 

 excrementitious matter in the nest, rather than the living young? If we 

 could hold to this view we would have an explanation of the excellent 



