OYCLORHAPHA ASCHIZA. 
611 
their breathing stigmata at the end of very long extensible tubes so as 
to reach the surface while the animal is feeding below (fig. 404) ; the 
larvse of Volucella live in the nests of bees and 
wasps, possibly playing the part of scavengers 
there, and the extremely close likeness of some 
of the adult flies to bumble-bees is one of those 
facts of resemblance which lack a satisfying 
explanation. The very curious round flat larva 
of Microdon , the fly shown on PL LXY, fig. 6, 
similarly lives in ants’ nests, but the ants have 
been observed to actively resent the presence 
of the ovipositing female. Flies of this genus 
are not rare in the hills, and here again the 
likeness to a bee found in the same locality is 
noticeable. The chief interest of the family 
economically lies in the fact that the larvae of 
a number of Syrphids feed exclusively on the 
Aphidce which do so much damage to plants 
of various kinds. The parent fly may some- 
times be seen hovering about and laying its 
eggs on plants infested with Aphids. The eggs 
are long, oval, rather larger at one end, and are 
often adorned with a sculptured pattern. The 
larva (PL LXIY) has a thickish often rather 
transparent body tapering in front, generally with the posterior stigmata 
at the extremity of a short thick tubular excrescence, and a small very 
mobile eyeless head which moves here and there in search of food in the 
shape of Aphids. The creatures possess a very large appetite, and the 
work of destruction accomplished by them must be far from insignificant. 
When the larva is full grown the larval skin hardens and forms a case 
or puparium enclosing the true pupa, and from the head of the latter two 
little horns usually project through the outer case. Though the fracture 
of the puparium is Cyclorhaphous, it appears that these flies do not use 
the ptilinum to push off the top piece as do the Muscoids, and the 
well-marked frontal suture of the latter is not present, there being only a 
small triangular area above the antennae, often quite inconspicuous, called 
the “ frontal Sun ale.” The pupae of the aphis-eating Syrphids may not 
Fig. 404 —Pupating larva 
of Eristalis. (x2.) 
