322 REPORT OF THE COMMISSIONER OF AGRICULTURE. 



THE CABBAGE OSCINIS. 

 (Oscinis brassicce n. sp.) 

 Order Diptera; Family Oscinedje. 

 [Plate Vm, Fig. 5.1 



On June 17, 187G, we noticed that in the vicinity of Saint Lonis cer- 

 tain cabbage-leaves were mined by the larva? of some insect. Upon 

 opening the mines, however, nothing was found but a number of Hymen- 

 opterous pupie, undoubtedly of parasites upon the original miner. A. lew 

 days later the mining larva was found. It was Dipterous, pupated un- 

 der ground, and a single fly was bred June 30. In 1882 (June 25) the 

 same insect was found mining cabbage leaves in Georgetown, D. C. 

 At this time the larvae were all full-grown and pupated two days later, 

 about a quarter of an inch under the surface of the ground, where all 

 the specimens died. The mine is an irregular pale trail, ranging from 

 0.5 mm to 2 mm in diameter, often turned on itself and coalescing to form 

 irregular patches and with dark excrementitious points. The miner is 

 a light yellowish green maggot with black mouth-parts. 



Although this insect seems rare at present, it may at any time be- 

 come sufficiently numerous to prove injurious, and it is well to study it 

 in advance. It seems closely related to the Clover Oscinis ( Oscinis trifolii 

 Burgess) treated in the Department Keport for 1879. As will be seen 

 from the above notes, we have no knowledge of the number of broods, 

 but. judging from analogy, there are probably at least three annual gen- 

 erations, and the insects winter underground in their puparia. 



DESCRIPTIVE. 



Oscinis BRASSIC2E n. sp.— Closely resembles Oscivis trifolii Burgess. Differs only in 



the folio-wing particulars : The eyes are narrowly margiued with black, the border 

 at apex being pronounced and wide. The scutellar spots are narrow, not so wide as 

 in trifolii. Abdomen yellow only on venter, not margined with yellow. Middle and 

 hind tibiae pronouncedly fuscous. Third and fourth wing- veins more widely divergent 

 than in trifolii. 

 Described from 1 9 , June 30, 1876, Saint Louis, Mo. 



Larva. — Length of full-grown larva 4.19 mm , width of penultimate joint 0.9 mm . 

 Color light yellowish-green. Skin nearly smooth, the raised junctures of the seg- 

 ments each marked with from 6 to 12 transverse lines of minute granulations. The 

 head is difficult to observe, as it is usuaDy withdrawn with the prothoracic joint 

 into the meso-thoracic joint. It is pointed anteriorly, and the characteristic black 

 rake, with its eight teeth, forming the mouth-parts, is plainly seen even when the 

 head is entirely telescoped. The prothoracic spiracles are mounted on short, stout 

 tubercles, which are proportionately smaller than those of trifolii. The anal joint 

 appears very bluntly rounded, not sharply and obliquely truncate as with trifolii and 

 malvce. The anal spiracles are mounted on long, slender papillae, directed backwards 

 and parallel with each other. The penultimate joint bears four very stout, conical, 

 tubercles directed posteriorly, two of which are subdorsal and two sublateral ; also 

 two smaller, subventral tubercles. The anal joint can be drawn partially within 

 the pre-anal, and when its protruding papillai are added to the large tubercles of the 

 latter joint the posterior end of the body seems to fairly bristle with points. 



Puparium. — Length 2 mm . Broadly oval seen in dorsal profile; convex above and 

 flattened below. Color, brown when living and nearly white after the fly has issued. 

 The prothoracic and anal spiracles project at either end, but are not so prominent as 

 with trifolii. The skin is smooth, and but ten joints show. 



