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 

 covered with them ; they hung from the legs and antennae 

 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 Ocarina (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 



a DC Geer vii. 120. 



