224 DISEASES OF INSECTS. 



The observations of naturalists have chiefly been con- 

 fined to the Hemipterous genus Aphis ; but these early 

 attracted their notice. Leeuwenhoek has given a par- 

 ticular and entertaining account of the proceedings of 

 /. Aphidum. As soon as the little flies approached 

 their prey, they bent their abdomen, which is rather 

 long, between their legs, so that the anus projected be- 

 yond the head ; then with their ovipositor they pierced 

 the body of the Aphis, at the same time carefully avoid- 

 ing all contact with it in every other part : whenever they 

 succeeded in their attempt, a tremulous motion of the 

 abdomen succeeded. Only a single egg is committed to 

 one Aphis : when hatched, the latter becomes very 

 smooth and appears swelled ; it is, however, full of life, 

 and moves when touched. Those that are thus pricked 

 separate themselves from their sound companions, and 

 take their station on the underside of a leaf. After some 

 days the inclosed grub pierces the belly of the Aphis, 

 and attaches the margin of the orifice to the leaf by silken 

 threads ; upon this it dies, becomes white, and resembles 

 a brilliant bead or pearl a . De Geer observed also an 

 Ichneumon on the Coccus of the elm, /. Coccorum*. 



Amongst the Neuropterous tribes likewise, probably 

 the Ichneumonidce commit their usual ravages ; but their 

 exploits, as far as I recollect, have met with no historian. 

 I have a small species related to Chelonus, which a me- 

 morandum made when I took it tells me was obtained 

 from JEshna viatica ; yet I do not remember ever tracing 

 that species to its final change, so that I must have taken 

 this Ichneumon from the perfect insect. It suffices, how- 

 ever, to prove that this tribe is also exposed to the at- 



3 Leeuwenli. Epist. Oct. 6, 1700. De Geer ii. 869. 

 * Jbid. i. G04. 



