DIPTERA. 
6 3 
commonly known as rat-tailecl maggots, on account of the long tail-like appendages 
at the hinder end of the body. With this flexible and telescopic tail, traversed by 
tracheal tubes opening at its tip, the maggot is able to breathe while below the 
water, by keeping the tip of its tail above the surface, where it is supported by 
the rosette of hairs round the extremity. The eggs of drone-flies are also laid in 
dead carcases and other refuse, and it is now believed that the legend of the ox- 
born bees of the ancients is traceable to this habit of the fly, in conjunction 
with its striking resemblance to the honey-bee. The belief that honey-bees are 
produced by spontaneous generation from carcases of dead animals has pre¬ 
vailed for more than two thousand years, but according to Osten Sacken, “ the 
original cause of this delusion lies in the fact that a drone-fly (Eristalis tenax ) lays 
its eggs upon the carcases of animals, that its larvae develop within the putrescent 
mass, and finally change into a swarm of flies, which in their shape, hairy clothing, 
and colour look exactly like bees, although they belong to a totally different order 
of insects.” Scarcely less interesting than the drone-flies are the species of 
Volucella. These large flies (p. 65, No. 9) mimic humble-bees in colour and form ; 
and it was long supposed that the females were thus enabled with impunity to 
enter the nests of humble-bees and lay their eggs amongst those of the proper 
owners. But although it is true that the eggs of the Volucella are laid and the 
larvae reared inside the nests of various Hymenoptera, it has been ascertained that 
the species which resemble humble-bees visit for the same purpose the nests of 
wasps, to which the flies bear no particular resemblance. And it is hardly credible 
that the wasps give access to the flies under the delusion that they are members 
of the community, as was conceivable in the case of the bees. We are compelled 
therefore to conclude that the flies are allowed by the bees and wasps to come and go 
without interference for some reason apart from the resemblance that exists between 
the two sets of insects. It is, of course, possible that the similarity offered by the 
flies to bees and wasps is more deeply seated than was supposed, and affects such 
senses as touch or smell, or some other unknown sense, but there seems no evidence 
to justify this supposition ; and if the maggots of the flies feed on the larvae of the 
bees or wasps, we are not yet in a position to offer an explanation of the pheno¬ 
menon. If they play the part of scavengers, clearing the hive of waste matter, the 
reason for the admittance of the flies becomes clear. 
Closely resembling many of the Syrphidce in their banded coloration, 
which imparts to them a wasp-like aspect, the members of the family Conopidcc 
may be recognised by the absence of the spurious vein in the wings, and also by 
their broad heads, of which the fore-part is produced into a conspicuous promin¬ 
ence bearing the long antenna?. Like the horse-flies, the Conopidcc in the adult 
stage frequent flowers, but they lay their eggs in the bodies of various Hymen- 
optera, like bees and wasps, and also in crickets and other Orthoptera. Here 
the eggs hatch and the larvae feed upon the living tissues of their prey, and 
here they undergo their metamorphosis, although they do not invariably 
quit the place of their development upon the death of the victimised host. 
Taschenberg, for example, found the pupa of Conops vittatus emerging from 
the abdomen of a humble-bee which had been for six months in his collection. 
The Conopidcc are widely distributed, and especially abundant in the tropics. 
