Notes on Brachycentrus Nigrisoma 



Banks'"' 



J. T. LLOYD, 

 ITHACA, N. Y. 



The larvae of Brachycentrus nigrisoma Banks, Trichoptera of the 

 family Sericostomatidce, are dwellers in limited areas of the large 

 spring-fed brooks in the McLean Bogs, near Ithaca, N. Y. Here, 

 with their symmetrical cases firmly cemented to some solid support 

 and opening against the swift current, the larvae wait for some frag- 

 ment of food to float within their powerful grasp. 



Habitat: The larvas are locally distributed in limited areas of 

 Bear Creek, McLean, but are very abundant in the areas which they 

 inhabit. 



Larval Habits : The larvae live sedentary lives with one edge of 

 the large end of their cases firmly cemented to submerged rocks or 

 sticks. Always they inhabit positions on the exposed surface of their 

 support and always they face the unbroken current. While waiting 

 for prey they assume the position shown in Figs. 6 and 8, protruding 

 their heads slightly and extending their prothoracic legs straight 

 forward. The mesothoracic legs are held upward while the meta- 

 thoracic legs are extended to the sides. From this position they 

 eagerly seize and quickly devour small larvae or bits of vegetation 

 that float within their grasp. 



In the unnatural conditions of still-water aquaria in the laboratory 

 they attach their cases and assume their characteristic attitude of 

 outstretched arms. If a particle of food material be moved within 

 their grasp it is eagerly seized and devoured, but if, however, the 

 food be placed in front of the larva, even in contact with its limbs 

 or jaws, it is ignored or pushed aside. Apparently the larva does 

 not recognize food that is not moved into its grasp. From time to 

 time larvae confined in aquaria detached their cases and moved from 

 place to place. It seems probable that the larvae in the streams. 



*Contribution from the Limnological Laboratory of the Department of Entomology in 

 Cornell University. 



