42 Psyche [April 



small pieces of chitin, often covered with hairs. Some of the 

 pieces belonged to small gnats allied to the Chironomidse. In 

 one case a mandible of some small insect larva was found among 

 the fragments. No traces of vegetable matter could be detected. 

 As the head and mouthparts of the larva are extremely small it 

 seems very unlikely that it can seize and dismember active, living 

 prey. It is much more probable that small flying or creeping 

 insects are caught and killed or disabled in the glutinous web 

 and then leisurely devoured by the larva when it comes upon them 

 in its wanderings along the threads. Hudson rejects this supposi- 

 tion on what appears to us to be rather feeble negative evidence. 

 The nature and arrangement of the web certainly indicate that it 

 is used as a trap. He describes it as follows in his second paper 

 (1891): "The web referred to above is suspended in a rocky or 

 earthy niche in the banks of streams in the densest parts of the 

 forest. It consists of a thick glutinous thread stretched across 

 the niche, and supported by several smaller threads running right 

 and left, and attached to the sides and end of the cavity. On 

 this the larva invariably rests, but when disturbed immediately 

 glides back along the main thread, and retreats into a hole which 

 he has provided at the end of it. From the lower side of this 

 central thread numerous smaller threads hang down, and are 

 always covered with little globules of water, resembling a number 

 of minute silver-beaded necklaces, constituting a conspicuous, 

 though apparently unimportant, portion of the insect's web." 



That the web must serve as a trap is suggested also by O. F. 

 Cook's recent description (1913) of a similar though more elaborate 

 structure spun by what is in all probability a Mycetophilid larva 

 in the caves of Alta Verapaz, Guatemala. In this case the gluti- 

 nous web is figured and described as resembling "the rope signals 

 that are hung near bridges and railroad tunnels to avoid accidents 

 to train-crews." Cook found embedded in the slimy threads 

 several small insects such as mosquitoes and other soft -bodied 

 species and even a small beetle, and believes that these constitute 

 the food of the larva. 



LITERATURE CITED. 



1913. Cook, 0. F. Web-spinning Fly Larvte in Guatemalan Caves. Journ. 

 Wash. Acad. Sci., Ill, 1913, pp. 190-193, 1 fig. 



