108 



Observations on the various Insects 



the pupae cases are sometimes found in multitudes under the 

 boards. 



From the large quantities of these maggots which have been 

 ejected from the human stomach and intestines, accompanied by 

 the most distressing symptoms,* I am led to conclude from their 

 economy, that the eggs or larvae are conveyed into the stomach in 

 badly or half-cooked vegetables, for it is evident they subsist upon 

 decomposing vegetables and excrementitious substances, and I 

 have found similar but very small larvae on cabbage- leaves in 

 October. It is therefore very probable that under certain mor- 

 bid conditions of the constitution they are able to live in the 

 human body until they have arrived at their full growth, when 

 they are necessarily ejected to become pupae, and after a short 

 time to be transformed into flies. It is not a little remarkable 

 that the maggots of Musca stabulans should have been also voided 

 from the intestines,^ and that fact tends to substantiate the view 

 I have taken of the subject, and the cause of their presence in the 

 human system, for that is the other species of large fly which I 

 bred from maggots generated in the same potato. 



I also detected the larvae and pupae of a smaller species of fly 

 called Drosophila, which hatched the middle of August with the 

 foregoing insects. They are also inhabitants of cellars, as their 

 specific name implies, where the larvae are usually very abundant 

 all the year round. They will breed in stale beer, and probably 

 are generated where there is any leakage from the tap and oozing 

 about the bung, as well as from the fungi which spring up round 

 rotten wood, &c., in cellars. I have also known them to be 

 bred from vinegar^ and it will be remembered that one species, 

 D.flava, lives on the pulpy substance of the turnip-leaves, § and 

 another, D. graminum, 1 have bred from cabbage-leaves. In 

 spring and autumn the flies abound, and are not unfrequently on 

 the inside of our windows. They belong to the Family Mus- 

 cid^e, and the Genus Drosophila. That bred from the pota- 

 toes appears to be the Linnaean species named 



36. Drosophila cellaris. It is line long, and expands 4 

 lines : the general colour is ochreous : the head is broad as well 

 as the face, in the centre of which are inserted the 2 little droop- 

 ing pubescent horns, the 3rd joint is oval, and from the back 

 arises a feathery bristle jointed at the base : the orifice forming 

 the mouth is very large ; eyes large, hemispherical ; ocelli 3 on 



* IlifF, in Lancet for July 25th, 1840 ; Trans. Ent. Soc, vol. ii. pp. 152 

 and 256, pi. 15, f. 19 ; Memoirs of Med. Soc. of London for 1789, vol. ii. 

 f. 1—4. 



t British and Foreign Medical Review for April, 1842. 



% Curtis's Brit. Ent., fol. and pi. 473, and Curtis's Guide, Genus 1334. 



§ Journal of Royal Agric. Soc, vol. Hi, p. 69, pi. D. f. 30. 



