2/8 E. GABRITSCHEVSKY. 



abdominal segment extend also partly onto the second ring, and 

 sometimes on to the upper quarter of the fourth abdominal ring. 

 The last segments are yellow pilose or reddish. An increase of 

 black hairs on thorax, scutellum and abdomen is also charac- 

 teristic for the endemic bumblebees. Bombus vosnesensky (PL 

 IV., 6), B. Crotskii (PI. IV., 7), B. californicus (PI. IV., 8-11) are 

 good examples of this. Volucella facialis is distributed along the 

 Pacific coast and in Alaska. The coincidence in the distribution 

 of black and yellow bands in Volucella flies and bumblebees 

 of this zone is not absolutely exact, but yet the increase of the 

 black hairs and the distinct and parallel process of melanization 

 in both insect genera is strikingly evident. 



Volucella B. facialis lateralis (PI. I., n). 



This fly is extremely like the former one, but the pleura are 

 yellow pilose, and the black spot on the dorsum of the thorax has 

 a more reduced area than in V. facialis. V. lateralis belongs to 

 the Canadian zone (Alaska to Newfoundland, Mt. Desert) and is, 

 so to speak, the eastern representative of facialis. I have no data 

 as to other flies and bumblebees of this large area, and a com- 

 parison has thus been impossible. 



SUMMARY. 



1. The European Syrphid fly Volucella Bombylans and its 

 varieties, V. haemoroidalis and V. plumata have a coloration which 

 corresponds to the coloration of the majority of European bum- 

 blebees. The same is true of many other pilose flies of Europe. 



2. The Caucasian Volucella bombylans caucasica has a color- 

 ation which corresponds to the coloration of various bumblebees 

 of this mountain region. The same is true for other pilose flies 

 of this zone. 



3. The American Volucella bombylans evecta-americana of the 

 eastern states and 8 other species of Syrphid flies have exactly the 

 same color patterns as six different Bombus species of this region; 

 four different Bombus of the same area have' the same type of 

 coloration as three other beelike flies of the eastern states. 



4. Volucella bombylans evecta sanguinea, and Eristalis flavipes 

 var. melanostoma of the eastern states are rare and parallel 



