13G DIPTERA OP NORTH AMERICA. [PART III, 



coalesce into an incomplete crossbaud. The tip of all the tibiae, a ring 

 on the middle of the hind ones and the tip of all the tarsi, black. Long. 

 corp. 0.21 ; long. al. 0.20. 



Unfortunately, I possess only a single, badly preserved speci- 

 men of this insect. The resemblance to the preceding species 

 is so great, that only the observation of the living insect or 

 the comparison of a large number of specimens, will enable one 

 ultimately to decide about their specific diversity. The con- 

 siderably larger size, the darker coloring of the picture of the 

 wings, the coalescence of the third crossband of the wings with 

 the infuscation on the posterior crossvein into a complete band, 

 the difference in the coloring of the feet (in S. cribellum the 

 tibia? show only a weak trace of a darker coloring at the tips, and 

 there is no trace whatever of a ring on the hind tibiae, the tarsi 

 are but slightly infuscated towards the end) — all these differences 

 render a specific distinctness probable, although, on the other 

 hand, the great resemblance of all the other characters tends to 

 diminish this probability. 



Hab. Middle States (Osten-Sacken). 



Observation. — In case the specific identity of S. cribellum and 

 cribrum is proved, the latter name should be retained for the 

 species, as representing the more fully colored, and hence, normal 

 specimens, while S. cribelluyn would then be regarded as a 

 smaller and paler variety. 



3. S. corticalis Fitch in litt. % 9 .—(Tab. VIII, f. 28.) Fusco-nigra, 

 polline albo-cinereo aspersa, punctis, muculisque fusco-nigris variegata ; 

 alae albido-hyalinae, venis omnibus, maculisque numerosis nigris. 



Brownish-black, covered with a whitish-gray pollen and with brownish- 

 black spots and dots ; wings whitish-hyaline, with black veins and 

 numerous black spots. Long. corp. % 0.15; £, 0.19. Long. al. 0.17. 



The ground color of the body is an opaque brownish-black. 

 Head of the same coloring, only the front, towards its anterior 

 margin, seems to have a more or less reddish-brown or brownish- 

 red ground color; the pollen on the whole head is whitish-gray; 

 on the extreme lateral margin of the front it is more dense and 

 almost white ; upon the middle of the front and at a considerable 

 distance from its sides, there are two oval, oblique, opaque, 

 brownish-black spots; a spot of the same coloring surrounds the 

 ocelli, and has, upon each side a smaller spot, upon which the 



