DISEASES OF INSECTS. 239 



How long it can retain this property remains to be as- 

 certained. 



De Geer states that he had seen them of the length of 

 two feet a ; but they vary considerably in this respect. In 

 ants, in which Gould detected them, he states their 

 length to be not more than half an inch b . In caterpil- 

 lars, which they sometimes infest, they are longer ; in 

 that of Notodonta Ziczac, De Geer found one three inches 

 and a half long c ; and Rosel three, of six inches, in that of 

 Deilephila Euphorbia d ; and in Phalangmm cornutum, 

 according to Latreille, they extend to more than seven 

 inches e . In the larva of a Phryganea L. the author 

 first named found one which was more than a foot long, 

 corresponding exactly with the Gordius aquaticus of 

 Linne ; being forked at one extremity, brown above, 

 gray below, and black at each end f . These animals ap- 

 pear to die as soon as they leave the body s they have 

 preyed upon ; except this happens in water, when their 

 activity has no repose. In this element they give their 

 bodies every possible inflexion, often tying themselves 

 in knots in various places, interlacing and twisting them- 

 selves in a hundred different ways; so that when con- 

 fined in the body of an insect, from their extreme sup- 

 pleness and power of contortion they find sufficient space 

 wherein to pack their often enormous length 11 . Linne 

 makes one of their habitats clay ; and Mr. W. S. Mac- 

 Leay finds them very common at Putney in clay at the 

 bottom of pools. 



2 De Geer ii. 556. b Gould Ants y 63. 



De Geer i. 551. d Rosel I. iii. 20. 



e Latr. Fourmis, 373. 



' De Geer ii. ubi supr. t. xiv./. 1214. Ibid. i. 553. 



h Ibid. ii. 556. t. xiv./. 12,13. 



