2J4 E - GABRITSCHEVSKY. 



As a rule, it is possible to maintain that most of the bumblebees' 

 males are like the Criorhina flies. This is due to the fact that the 

 males, like these flies, have reduced black bands which make 

 them almost indistinguishable. 



From the above we might infer that there is a very close 

 resemblance between bumblebees and flies of the eastern parts of 

 the United States. Yet it would be a mistake to conclude from 

 this that there is mimicry between both genera; it must not be 

 forgotten that there is also the same convergence in coloration, 

 even as regards details, within the group of bumblebees and also 

 within the group of flies or, more exactly, there is not only a 

 correspondence between the flies and bumblebees of a given 

 district, but the several species of Hymenoptera found living in a 

 region resemble one another closely, and species of flies are also 

 much alike among themselves. For example, when the bumble- 

 bees are compared with one another, we see that the coloration of 

 the variety of B. auricomus (PL III., 13, 14), with the yellow 

 scutellum, reappears in the same pattern in B. pennsylvanicus 

 (PI. III., 13, 14). One of the males of B. bimaculatus (PI. III., 

 9), is similar in this respect to one of the males of B. affinis (PI. 

 III., n). Many other coincidences are also evident and not 

 uncommon in these groups. (Compare figures.) The coloration 

 of the European B. lapidarius reappears in B. confusus, in many 

 other species and in Volucdla Bombylans (type) (PI. I., i). 



The distribution of V. b. evecta americana is probably by far 

 more restricted than that of the above mentioned bumblebees, 

 which may be found further to the south. This can be explained 

 through the fact that all large Volucella are circumboreal species 

 and never appear farther to the south than the 42d parallel, unless 

 there are mountains which extend to the south. Favorable 

 conditions are thus produced and the bumblebee nests may be 

 found again infested with Volucella larvae in more elevated zones. 

 Volucella evecta americana is not to be found much farther to the 

 north. According to Johnson this variety can be collected along 

 the Atlantic coast as far north as Mount Desert, but there this 

 fly is already replaced by Volucella bombylans facialis lateralis 

 (PI. I., ii), which belongs to the Canadian zone. 



