i86 Memoirs of the Indian Museum. [Voi,. V, 



Order DIPTERA. 



A large number of species of this order breed during the rains, and especially 

 after their cessation, when the water-level of the lake is sinking, in small pools near 

 the margin of the lake. In the waters of the lake itself we found, however, the 

 immature stages of only three flies — Eristalis arvorum, Anopheles rossii and a 

 species of Palpomyia. All of these were common in the right season at suitable 

 localities, the larvae of E. arvorum in decaying weed at the edge, those of the two 

 Nematocera among thickets of Potamogeton. The larvae of all three species are 

 evidently able to endure considerable changes in salinity. 



Family Syrphidae. 



1915. Eristalis arvorum, Fabricius, Brunetti, Rec. Ind. Mus. XI, p. 228 (pi. XI, figs. 8, 9). 



We have to thank Mr. Brunetti for identifying flies of this species, which he 

 states to be the commonest Indian representative of the genus. 



The larva (pi. xi, figs. 8,9) resembles the European species figured by Miall l , 

 but differs in the following points, — (i) the inner branch of the terminal part of the 





Fig. 3. — Eristalis arvorum, Fabricius. 



A. Lateral view of sensory papilla of larva : X75. 



B Spines on anterior extremity of body of larva : % 250. 



sensory papillae consists of two barrel-shaped segments, of which the basal one is 

 considerably the larger (text-fig. 3 A); (ii) the spines at the anterior extremity of the 

 body are bifid or trifid, except on the posterior part of the area they cover, where 

 they are simple (text-fig. 3B); (iii) there are about eleven chitinous ridges on each 

 side of the antechamber of the pharynx ; (iv) the posterior part of the body is 

 more densely covered with hair which extends on to the base of the tail ; (v) 

 the processes at the base of the tail are shorter and concealed by the hair. 



Flies of this species were observed in large numbers on two occasions, flying 

 round rocks at the margin of the lake and settling at the edge of the water, in March 

 near Patsahanipur and in November on Kalidai Id. The larvae were found among 

 rotting weed on both occasions. The species is widely distributed in the Oriental 

 region . 



1 Miall, Nat. Hist. Aquatic Insects, p. 198, figs. 70-77 (1895). 



