86 
BEITISH APHIDES, 
numerous, are effected in a manner very similar to the 
above. Kaltenbacb thinks that the larvae commonly 
take their persistent forms after their fourth moulting 
of skin. They then begin to multiply, and are 
from their condition of maturity well suited for 
description and reference. The young imagos, which 
have newly emerged from the pupa sheaths, usually 
exhibit delicate ground tints upon which the mark- 
ings contrast with much brilliance and sharpness. With 
age these colours sober down, and sometimes become 
very dark and suffused. The venation of the wings 
of the younger flies is also less pronounced in colour. 
Thus the ima.go of Dre^anosiplium platanoides emerges 
from its chrysalis almost entirely of a bright green, but 
after the lapse of a few hours, or days, the thoracic 
lobes become dark, the abdomen becomes barred with 
black, and the insect shows its adult colours. Ex- 
amples may be given also in which the pigmented 
markings finally obliterate the first prevailing ground 
tints. 
The alate females are never so plentiful as the ap- 
terous, except at the times of general migration in 
autumn or spring. Almost every individual then may 
be found either in the pupal or the winged condition. 
Aphides are somewhat heavy in flight notwithstand- 
ing their remarkably large expansion of wing. These 
organs seem to act principally as sails for purposes of 
suspension in the air. Their chief locomotion is effected 
by the winds, on which they travel for miles and some- 
times at a great height. When preparing for flight 
the wings are placed at right angles to the body for per- 
haps a second of time, and then the insects rise with 
numerous gyrations. Gliermes abietis throws itself upon 
its back and spins round violently with a considerable 
describes a similar process in tbe case of certain Ephemerae, wbicli, 
whilst under his microscope, required only ten seconds for their extri- 
cation from their pupae. As in Aphis, the imago appears to be separated 
from the pupa skin by a pellicle of air. A rent takes place in the 
thorax and the insect walks out, the wings rapidly expand, and flight 
is taken in an incredibly short time. 
