No. 3.] Calcutta Municipal Water. 189 



larva feeds on the old leaves, seeming to eat the under surface only. The case is 

 formed of minute particles of leaf attached to the outer surface of the silk cocoon. 

 When about to pupate the case is suspended by a white thread from a half to 

 one nnd-a-half times the length of the cocoon itself ; this thread has a few particles 

 of dried leaf usually attached along it. The moths emerge in August and 

 September, and probably at other times during the year. The female is a whitish 

 insect without any scale-covering, having the head -end produced to a slight hook, 

 the scutellate segments being shiny dark brown. The male has the wings entirely 

 sooty-black on the upper side, but with the under side of the hind wing milky-white, 

 with the exception of a dark band along the costa : the abdomen is slight, and the 

 wings rather rounded. The female lays her eggs in the cocoon, from which the 

 young larvae ultimately construct their first cases. " 



XI.— INSECT IN CALCUTTA MUNICIPAL WATER. 



Chironomus cubiculorum, Doleschall. Family Chironomidx. 

 Order Diptera. Plate xv, Figs. 5 b, larva] 5 c, pupa ; 5, male 

 imago ; 5 a, female imago. 



In December, 1900, the health authorities of Calcutta forwarded 

 large numbers of the larva of a dipterous insect, which they reported 

 were causing them some uneasiness as the larvae existed in countless 

 swarms in the filtering beds of the Calcutta water-supply. They proved 

 on examination to be the larvae of a species of midge (Family Chirono- 

 midse). They were reared, and as the Museum possessed no examples 

 of this family, the insects were forwarded to Mr. D. W. Coquillett, 

 who identified them as Chironomus cubiculorum^ Doleschall. 



As but little is known regarding this family in India, possibly due to 

 their being usually taken for mosquitos, to which they are very similar, 

 a short description of the larva and its habits may be of value. 



The larvse of the Chironomidse, unlike those of the Culicidas, are 

 not always found in water, but when they are, they can be distin- 

 guished from the larvae of mosquitos by their worm-like appearance, 

 the thorax not being conspicuous as in mosquito larvae ; besides 

 which they are not provided with the hairs with which the mosquito 

 larvae are somewhat plentifully clothed. The larvae of many species, 

 as in this instance, are red in colour, hence their popular name of 

 "blood worms/' this colour, it being of interest to note, being 

 produced by the presence of haemoglobin, which is present in those 

 species which have their tracheal system rudimentary. The oxygen 

 required for breathing being obtained in these species through the 

 haemoglobin, which possesses the power of assimilating oxygen. The 



O 



