THE ANATOMY OF A CHIRONOMID LARVA OF 

 THE GENUS POLYPEDILUM. 



By Baini Peashad, M.Sc, Superintendent of Fisheries, Bengal Fisheries 

 Laboratory, Indian Museum, Calcutta. 



(Plate XXIII). 



There has been an unfortunate confusion as to the generic name of 

 the larva here described. The adult fly reared from a similar larva was 

 orioinally named by Kiefler Chirononius fasciatipennis (4), and is referred 

 to under this name by Annandale (2), and also by Gravely (3). Kieffer 

 in a later paper (5) assigned the species to the genus Polypedilum Keift'., 

 and it must therefore be known as Polypedilum fasciatipennis (Kieff.). 

 It is impossible to be certain with our present knowledge of the Chiro- 

 nomid larvse whether the form that I am about to discuss is specifically 

 identical with the one from Calcutta, but no difference has been dis- 

 covered either in structure or in habits, and there is no doubt of the 

 generic identity. 



The specimens on which 1 have based my observations were taken 



in the Inle Lake, Southern Shan States, by Dr. N. Annandale and Dr. 



F. H. Gravely in February 1917. They were living among dense masses 



of weed {Ceratophyllum) in clear water. The habits of the Calcutta 



form as described by Annandale (1, 2) are as follows : — '' In the early 



stages of its larval life this insect wanders free among communities of 



pvotozoa {Vorticella, Epistylis, etc.) and rotifers on which it feeds, 



but as maturity approaches begins to build for itself a temporary shelter 



of one of two kinds, either a delicate silken tunnel the bottom of which 



is formed by some smooth natural surface, or a regular tube .... 



The tubuler shelters occasionally found are very much stouter structures 



than the tunnels, but are apparently made fundamentally of the same 



materials ; and structures intermediate between them and the tunnels 



are sometimes produced. The larva as a rule fastens to them branches 



detached from living colonies of Vorticellid protozoa such as Epistylis." 



In the Inle form the tube^ is made of a silky material and is closed 



at both ends, the larva however can come out of it at any point as the 



whole structure forms a loose net work. The tube is covered by a thick 



growth of a protozoan which has been identified as Epistylis pivicans by 



Dr. Ekendranath Ghosh. 



The larva) in their cases on being taken from the lake were put mto 

 a bowl of water, and it was observed that they began to devour the 

 Epistylis. The protozoa on this broke off from their stalks and swam 

 away. A small caddis-fly, of which vast swarms arose from the lake 

 every evening at the period at which the larvse were collected, dropped 

 its eggs into the bowl in which the larvae were living. These eggs were 



1 An enlarged photograph of the tul.c with its covering of protozoa is reproduced by 

 Dr. Annandale on pi. XXI of this volume. 



