THE VOLUCELLH. 
399 
evidently a change has taken place, for the larval condition is at 
an end. If one of these floating creatures be taken up and cut 
open, the pupa will be seen within the skin, which acts as the 
cocoon, and also as a boat for the fly which will spring into life 
in a short time. The fly, which has two perfect wings, a flat body, 
long antennae, and which is decorated with beautiful colours, is about 
as different an insect from the long-tailed, dull-coloured swimming 
larvae as can well be imagined. In the engraving opposite the 
perfect insects are seen in flight, and one is upon a rush ; two larvae 
are shown, one on the right hand side has its tail erect, and is 
breathing in air, and beneath the insect on the leaf, is a nymph. 
The Diptera with a short and thick trunk, mandibles united 
to form a single blade, and with a broad and very flexible lip, 
which makes a good sucker, are distinguished as Syrphidce. 
Their proboscis is thus long and membranous, and they like 
honey. There are several very interesting genera in this family. 
The Volucellce are large flies, which have black, yellow, and 
russet colours upon them, and they choose the nests of social 
bees for their larvae. The female deposits its eggs in the combs, 
and particular species have their favourite bee-hive or wasp nest, 
as the case may be. Thus Volucella bombylans visits the humble 
bees, and Volucella zonaria attacks the wasps, and curiously 
enough wears the livery of those dangerous insects, amongst 
which she leaves her eggs. The larvae of Volucella are of a dirty 
white colour, are covered with small spines, and the last segment 
of the body is rounded off, and is pierced for the organs of 
respiration. The membranous legs are furnished with little hooks. 
The egg is laid in the cell which contains the wasp larva, and 
when it is hatched the Volucella eats its way into its victim, and 
gradually intrudes the whole of its body except the last segment, 
which being in contact with the external air, and having the respi- 
ratory orifices in it, is the only portion of the body by which the 
parasite can be distinguished, and through which it can take in 
air to oxygenate its blood. 
When the Volucella larvae attain their full growth they are 
transformed into nymphs, which have two small open tubes placed 
upon the prothoracic region, and which communicate internally 
with the tracheae. This apparatus is like that of the gnat. 
