PACKARD.] POTATO-INSECTS. 737 



there is a little fleshy horn on each side ; on the following segment is a 

 spiracle on either side, surrounded by several stout short rays ; the two 

 next segments have tubercles on the back ; the remainder have a 

 double series down the center, producing bristles, with a double row 

 on each and eight of the segments have a pair of short spines 

 each beneath, which enable it to walk ; the apex is armed with six 

 long bristles a little spiny at the base, but most of the others are 

 naked, or with the slightest appearance of pubescence or little spines 

 at the base ; on the apical segment are two spiracular tubes. Tlie pui)a 

 being formed within the indurated skin of the larvai, it varies from it 

 only in being more convex above, and the fly esca[)es by a lateral open- 

 ing in the thorax. 



" These larvaB and purpaj I find occasionally in my garden where cab- 

 bages have long occupied the ground, and Dr. Harris remarks that the 

 hairy maggots of Anthomyia cunicularis, or an allied species, live in rot- 

 ten turnips; they also abound in privies, and the purpse-cases are found 

 in multitudes nuder boards. 



" From the large quantities of these maggots which have been ejected 

 from the human stomach and intestines, accompanied by the most dis- 

 trt^ssiug 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 excremeutitious substances, and I have found similar but very small 

 larvae on cabbage-leaves in October. It is, therefore, very probable 

 that, under certain morbid 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 pnpse, and after a short 

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

 maggots of Miisca stabulans should have been also voided from the in- 

 testines, 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 gen- 

 erated in the same potato. 



"I also detected the larvae and pnpse of a smaller species of fly called 

 Drosophila, which hatched in 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, etc., in cellars. I have 

 also known them to be bred from vinegar, and it will be remembered 

 that one species, B. flava, lives on the pulpy substance of the turnip- 

 leaves, and another, D. grandnum, I 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 Muscid^ and the 

 genus Drosophila. That bred from the potatoes appears to be the 

 Linnean species named 



"Drosophila cellaris. — It is 1^ line long, and expands 4 lines ; the general color is ochre- 

 0U8 ; the beacl is broad as well as the face, in the center of which are inserted the two little 

 drooping pubescent horns, the third joint is oval, and from the back arises a feathery- 

 bristle jointed at the base ; the orifice forming the mouth is very largo ; eyes large, hemi- 

 spherical ; ocelli three on the crown ; thorax globose-quadrate ; scutal semi-ovate'; abdo- 

 men small, depressed, oval, blackish, and six-jointed, with four or live ochreous bands; the 

 apex pointed in the female; wings incumbent in repose,. very long, and ample, yel- 

 lowish and iridescent, with a very short marginal cell, and four longitudinal nervures, 

 the second and third united toward the base, the third and fourth toward the mar- 

 gin ; balancers small, clavate ; six legs, tapering ; feet long, slender, and five-jointed, 

 terminated by minute claws. , 



47 G s 



