HABITS OF A DIPTERON PREDACEOUS ON MOSQUITOS. 281 



than the original one, very soon bit a hole through which more and more of the 

 Syrphid's viscera gradually protruded. Eventually this mosquito larva dropped 

 off and wriggled away, taking a small portion with it, much of which was consumed 

 at leisure. The Syrphid's struggles thereafter got more and more feeble and in 

 two or three minutes it straightened out and ceased to move, floating on the surface, 

 the first mosquito larva still holding to it. An attempt was then made to secure 

 this larva, which however alarmed by the movements of the numerous Culex larvae 

 through the water being disturbed by the net, suddenly let go and vanished. The 

 precise species of larva is therefore impossible of determination ; all that can be 

 recorded in referrence to it is that it was considerably larger than any of the Culex 

 larvae ; it had posterior respiratory spiracles only ; it also suspended itself in 

 the water rather more obliquely than the Culex larvae did.* It was not possible 

 to capture any with the means at one's disposal. 



Such a fate for these Syrphid larvae would seem to be by no means uncommon, 

 for on the following morning two more, both dead and with viscera protruding, 

 were seen floating on the surface. One rather wondered how it was that any of the 

 Syrphid larvae, which were securely grouped on a piece of rotting cassava one 

 and a half inches below with their tubes thrust up to the surface, ever came up 

 to the top, thereby incurring such risks. The explanation is probably to be found 

 in the occasional failure of the larvae to withdraw their life-lines from the surface 

 in sufficient time to escape the sudden attack of the mosquito larvae and in their 

 subsequent endeavours to set themselves free. 



When the sun was ofl the pool full-fed Syrphid larvae, with their tails already 

 partly shrivelled, were seen to crawl out and to burrow in dry sand well above 

 waterline, where their puparia were readily obtained. Some of these larvae placed 

 on 12th September in a box containing dry sand pupated in about forty-eight hours, 

 and the flies emerged on about 23rd September, the pupal stage having therefore 

 occupied about twelve days. The species has been identified by the Imperial 

 Bureau of Entomology as Phytomia curia, Lw. During the heat of the day these 

 flies were frequently seen ovipositing in the wet sand at the margin of the pool. 



[The fact that Lispa preys on mosquito larvae has also been recorded by 

 Mr. J. Mitford Atkinson ( Jl. Trop. Med. xii, 1909, pp. 255-6 ; Howard, Dyar & Knab, 

 Mosquitoes of N. America, i, 1912, p. 170), who in Hong Kong observed Lispa sinensisy 

 Schiner, devouring larvae almost as long as their own bodies. — Ed.] 



* [The predaceous larvae were probably either Toxorhyncliites brevipalpis, Theo., or 

 Culex tigripes, Grp., both of which are known to prey on other mosquito larvae. — Ed.] 



