344 Prof. Miall and Mr. R. Shelford on the Structure and 
mentary canal; they give a green tinge to young larvee 
when seen through the semi-transparent body-wall, 
especially from the underside. Older larvee are more 
opaque, and of a brownish-green colour, with a pale 
and indistinct striping; the ventral surface of such 
larvee is white. Full-grown larvee are about an inch 
long. They are distinguished at a glance from other 
Dipterous larve by the long, transparent processes, 
which stand out from every surface. The larva is ex- 
tremely sluggish, remaining almost motionless for hours 
together. It clings to a moss-stem by its large anal 
hooks, and, thus secured, it may at times be observed to 
sway its body from side to side, as if to promote respira- 
tion. It creeps from stem to stem by grasping with the 
mandibles and the anal hooks alternately. When 
alarmed, it curls itself up like a caterpillar. Hcto-para- 
sitic organisms, such as Algze, Diatoms, and Infusoria, 
often attach themselves in great numbers to its skin, and 
especially to the outstanding processes. A small Plan- 
orbis has been found creeping upon it, and probably 
feeding on the vegetable growths. These parasitic 
organisms, together with the general colour of the body 
and the form of the numerous filaments, give the larva a 
strong protective resemblance to the moss among which 
it dwells. Even when held up against the light it 1s not 
easily distinguished from the leafy stalks of the moss, 
and in the darkness of a weedy pool it must be altogether 
invisible.* 
De Geer, who gives a good account of all the stages of 
Phalacrocera, with many illustrative figures (Mém. Hist. 
Ins., vi., p. 351, pl. xx.), tells us that the larva can 
endure long and severe cold. Being obliged to shut up 
his country-house, he left four of the larvae to the mercy 
of a Swedish winter. ‘lhe water by which they were 
surrounded froze at once to a solid mass. On returning 
in the following May, De Geer found the ice melted and 
half-evaporated. ‘Two of the larve still survived, and 
were able to creep about and devour fresh food. Before 
the end of May both of them pupated. 
The head can be completely retracted into the first 
and second thoracic segments, and is usually so retracted, 
* Mr. Scherren recommends the collector to pull out a mass of 
vegetation, and shake it over a piece of mackintosh. 
