DISEASES OF INSECTS. 235 
by means of a long anal pedicle by which it is attached 
to them. De Geer found these in such numbers upon 
a species of Leptura, that its whole body was almost 
covez'ed with them ; they hung from the legs and antennas 
in bunches, and gave the animal a most hideous and dis- ' 
gusting appearance. Under this load of vermin it could 
scarcely walk or move, and all its efforts to get rid of 
them were in vain : many were attached to its body and 
to each other by their anal pedicles, but others had cast 
them off and were walking about. When put into a 
glass with earth, they began to abandon their prey, so that 
in a few days it was quite freed from its plagues. He 
found that these parasites lived long in alcohol a . 
If you inquire — How are these mites originally fixed by 
their pedicles ? it seems most probable, that as the He- 
merobii, when they lay their eggs, know how to place 
them upon a kind of footstalk, so the parent Uropoda 
has the same power ; and this pedicle appears to act the 
part of an umbilical chord, conveying nutriment to the 
foetus not from a placenta^ but from the body of the in- 
sect to which it is attached ; till having thus attained a 
certain maturity of growth and structure, it disengages 
itself and becomes locomotive. Many eggs of the aqua- 
tic Acarina (Hydrachna, &c.) are also furnished with a 
short pedicle by which they are fixed to Dytisci and 
other water insects. De Geer found some of this de- 
scription on the underside of the water-scorpion, so 
thickly set as to leave no void space : they were oval, of 
a very bright red, and of different sizes on different indi- 
viduals; whence it was evident that they grow when thus 
' De Geer vii. ]2(i — . 
