DISEASES OF INSECTS. 229 
in books—occasionally is parasitic upon flies, especially 
the common ‘blue-bottle-fly (Musca vomitoria). They 
adhere to it very pertinaciously under the wings; and if 
you attempt to disturb them, they run backwards, for- 
wards, or sideways, with equal facility. 
2, We now come to a perfectly distinct tribe of in- 
sect parasites, which belong to that section or order of 
intestinal worms which Rudolph has denominated En- 
tozoa nematoidea, and Lamarck Vers rigidules*. To 
this tribe belong the Gordius of Linné and the Filaria 
of modern zoologists, which from the experiments and 
observations of De Geer, Dr. Matthey, &c. appear to have 
been too hastily separated, being really congenerous, and 
living indifferently in water and in the intestines of in- 
sects and other animals®. To this genus belong the 
guinea-worm (Gordius medinensis L.°), the Furia infer- 
nalis L., and several others that are found in various 
vertebrate animals. ‘These little worms have been dis- 
covered in insects of almost every Order; and their at- 
tack generally produces the death of the animal, though 
they appear not to devour those parts that are essential 
to life’. I once took a specimen of Harpalus azureus, 
- and upon immersing it in boiling water I was surprised 
to see what at first I mistook for an intestine, thrust itself 
forth; but upon a nearer inspection, to my great sur- 
prise I found it was one of these worms, thicker than a 
horse-hair and of a brown colour. Mr. W.S. MacLeay 
* Lamarck Anim. sans Vert. 11. 196. 
> De Geer ii. 554—. Pictet Bibliotheg. Univers. num. ult. 
. © The existence of this animal has been satisfactorily ascertained 
by M. de Blainville, who had a specimen, extracted from a human 
body, sent him by M. Girard, a surgeon of Guadaloupe. 
4 De Geer ii. 555. 
