Syrphus. 271 



(puparium) is elongately ovate, arched above, somewhat flat belovv, 

 broad and rounded in front, more or less tapering behind; it is some- 

 times longer and more droop-like (in the narrow-bodied species); it 

 has of course the same dermal structure as the larva, only it is gener- 

 ally less pronounced, and the larger warts, vvhen such are present, 

 are smaller and more contracted. The anterior larval spiracles are 

 generally not to be seen, but the posterior process is present as in 

 the larva. The colour is similar to that of the larva, but it is often 

 altered as the development of the imago proceeds, because the colours 

 of the imago shine through the puparium. — The larvæ are all 

 aphidiphagous and are found on the leaves and stalks of various 

 piants arnong Aphides infesting these; most species may be found on 

 many various piants and evidently feed on many different species of 

 Aphides; De Geer mentions about S. lunulatua'^ (pinastri), which he 

 took on Pinus, that he fed it with various other Aphides. The larvæ 

 are very voracious; I once had a larva of S. nitens, which in six days 

 devoured so many Aphides that the vvhite, empty skins of these latter 

 formed at thick layer on the bottom of the bottle, the larva was in 

 these days grown to the double size. It is interesting to examine the 

 larva when feeding; it is generally sitting in a colony of Aphides, it 

 then stretches and raises the fore part of its body and bends it down 

 to different sides until an Aphld is touched, it then pierces it w'iih 

 the mouth hooks, detaches it with a jerk, and with the fore part of 

 the body in a raised position it sucks it out by a pumping action; 

 the Aphid is seen to become white, and is quite sucked in one or a 

 few minutes and it is then thrown off by a small jerk and the action 

 is repeated. Sometimes larvæ have been observed to attack and suck 

 other larvæ of their own kind, such as is also the case with Lasioph- 

 thicus. The pupa is generally found on leaves or stalks, attached by 

 some glue with the hind part; they may also sometimes be found 

 among old leaves or in flood refuse. With regard to the hibernation 

 it is, I think, the larva which hibernates, perhaps also sometimes the 

 pupa as mentioned by De Geer about S. lunulatus? (pinastri), but 

 this was in captivity ; above I have mentioned larvæ of S. ribesii found 

 on ^^li and on Vs, and of albostriatus found on ^"/i. Most species have no 

 doubt only one brood in the year, at all events with us, this is, I think, 

 especially the case with the special spring-species such as venustiis, 

 lunulatus, punctidatus and lasiophthalmus, and likewise with the species 

 occurring somewhat late as corollae, luniger, balteatus and I think 

 also auricollis; others may have two broods, as albostriatus. Most 

 species of the ribesii-^voup are on the other hånd more or less common 

 from early spring to late autumn, and their larvæ and pupæ may be 



