DESCRIPTION OF THE SPECIES. 255 



segment of the abdomen of the male is often clothed with alto- 

 gether black pile. Ovipositor red or brownish-red ; at its basis 

 two, sometimes confluent, black spots are visible ; the extreme 

 tip also is usually black; in length, the ovipositor hardly exceeds 

 the last two abdominal segments ; it is not very much attenuated 

 towards the end and is beset with black or blackish pile. Feet 

 altogether pale clay-yellow. Wings hyaline, with a black or 

 rather blackish picture; the outlines of this picture are sur- 

 rounded, in immature specimens, with a purer hyaline, in riper 

 ones, with a more whitish-hyaline hue; beyond this pellucid 

 border, the former kind of specimens show an indistinct, the latter 

 ones a more pronounced gray shade ; the picture of the wings 

 consists of four spots, very variable as to their size and the inten- 

 sity of their coloring; the first spot covers the stigma and usually 

 reaches only as far as the second longitudinal vein; the second 

 begins near the anterior margin immediately above the posterior 

 crossvein, thus leaving the tip of the marginal cell uncovered ; it 

 becomes narrower and more faint posteriorly, . thus reaching 

 more or less completely the anterior end of the posterior cross- 

 vein ; the third spot usually appears as a broad border along the 

 posterior crossvein and is more or less coalescent with the second, 

 forming a perpendicular crossband; the fourth spot lies upon the 

 apex of the wing and is more or less triangular, as its inner limit 

 runs perpendicularly from the tip of the second vein to the fourth 

 vein, which limits it posteriorly ; around the small crossvein and 

 in the environs of the root of the third vein there is a more or 

 less apparent, sometimes very distinct infuscation. 



Ilab. Canada (Mr. Provancher) ; common also in all Europe, 

 where the larva inhabits the flower-heads of different species of 

 Cirsium. 



Observation 1. — Europe possesses, besides the variety of this 

 species, discovered by Mr. Provancher in Canada, another form, 

 distinguished by considerably larger and darker spots* on the 

 wings. Specimens of both varieties might easily be taken for 

 different species; nevertheless, passages from one form to the 

 other occur in the picture of the wings, and I am not able to 

 discover between both the slightest plastic difference. In Ger- 

 mans Zeitschrift, Part V, Tab. I, f. 15, I have figured a wing of 

 the first variety. An extreme instance of the second variety is 

 figured in my Monograph : die Uuropdischen Bohrfliegen, Tab. 



