DIPTE11A. 
11L 
tended to its fullest length to receive the necessary 
oxygen from the air. The larvae of some of the Syr- 
phidae sometimes live in decayed trees. 
The genus Volucella contains some large flies, and is 
remarkable for the fact that the species belonging to it 
select the nests of bees, wasps, or hornets, wherein they 
deposit their eggs. Vollucella pellucens (Plate IV., Fig. 9), 
is a common species, and may be recognised at once by 
the first segment of the abdomen, which is white and 
pellucid ; it is a very swift-winged fly, and not very 
easily captured. The larvae of V. pellucens are parasitic 
on those of wasps; the larvae of V. bombylans on those 
of the bumble-bees ; this latter fly is very similar to a 
bumble-bee, and no doubt is not recognised by the bees 
themselves as being a dangerous enemy to their young, 
or they would not allow it to enter their nest. “ Did 
these intruders venture themselves among the bumble¬ 
bees in a less kindred form their lives would probably 
pay the forfeit of their presumption.” (Kirby and Spence). 
This is quite true of V. bombylans; but there is no 
resemblance between V. pellucens and any kind of wasp. 
The eggs are laid either in the cell which contains the 
wasp larva or on the top of the nest; the larva of 
Volucella , when hatched, eats its way into its victim, 
gradually intruding its whole body except the last 
segment, on which are the respiratory orifices, which 
thus come in contact with the external air. 
The insects of the next family, the Conopidce , frequent 
flowers, and their larvse, like those of the preceding one, 
are parasitic on those of the bumble-bees. They are 
generally slender insects, about half-an-inch long, with 
the second abdominal segment more or less petiolated. 
