276 E. GABRITSCHEVSKY. 



CONVERGENCE OF COLORATION BETWEEN FLIES 

 OF THE ARCTIC ZONE. 



Volucella bombylans arctica (PI. I., 17). This syrphid of the 

 evecta group is entirely dark yellow, with a short and unfinished 

 black band on the thorax. This Volucella is extremely like in 

 coloration to the arctic bumblebee Bombus gelidus (PI. IV., i), 

 and B. borealis (not figured). 



CONVERGENCE OF COLORATION BETWEEN FLIES OF THE ROCKY 

 MOUNTAINS AND BUMBLEBEES OF THIS REGION. 



The Volucella facialis Group, Volucella Bombylans facialis var. 



rufomaculata (PI. I., 13). 



Volucella rufomaculata, which is a parallel variation to the V. 

 evecta sanguinea of the evecta group is limited to the mountain 

 region of Colorado, Utah and New Mexico. The dorsum of the 

 thorax is black pilose-like in all varieties of the facialis group. 

 This is a characteristic which is entirely absent in the evecta group 

 (compare PI. II., 14-17). In this respect the male and female 

 flies of the evecta group are like the females of the European 

 varieties of Volucella Bombylans, and the male and female flies of 

 the facialis group can be compared to the males of the European 

 varieties of Volucella plumata and hxmoroidalis . The pleura of 

 the facialis flies are black as in the European varieties. It is not 

 improbable that the western American Volucella group is more 

 closely related to the European group. 



It is again striking that V. rufomaculata has a coloration 

 resembling that of most of the bumblebees of this mountain 

 region. An exact coincidence in color patterns can be observed 

 in Bombus sylvicola (PI. IV., 5), B. huntii (PI. IV., 1-2), B. 

 melanopygus (PI. IV., 4), B. eduardii (PI. IV., 13-17), B. ternarius 

 (PI. IV., 6). The same is true for the Asilid fly Dasyllis fernaldi 

 (PI. II., 18). 



Five other bumblebee species of the Colorado area, namely, 

 Bombus centralis (PI. IV., 18), B. borealis (PI. IV., 12), B. gelidus 

 (PI. IV., i), B.flavijrons (PI. IV., 7, 8), B. rufocinctus (PI. IV., 9), 

 B. kirbuellus (not figured), B. appositus (PI. IV., 12) have also the 

 same type of coloration with the characteristic rufous abdominal 

 segment like that of V. rufomaculata. The coincidence in 



