37i 



C R. OSTEN SAC'KEN'S PRODROME 



the latter specimen, the venter is almost entirely yellow, except at the extreme tip; in very 

 dark specimens it is almcst entirely black. The pattern of tlie Avings is remarkably uni- 

 form in all specimens. 



Male. Body altogether black ; abdomen, towards the tip with grayish golden hairs, 

 which, on the second, third, and fourth segments, form faint triangles; (in rubbed off 

 specimens a very fliint gray triangle is visiljle on the second segment). Venter black, some- 

 times brownish on the sides of the posterior margins of the segments, clothed with golden 

 haii-s, especially on the margins. The thorax is clothed with .black hairs; in some speci- 

 mens, however, rather numerous yellowish-gray hairs are mixed with them, in which case 

 the thorax somewhat resembles that of the female ; a trace of gray pollen is visible anteri- 

 orly. The pattern of the wings is like that of the female, only the brown of the two basal 

 cells is more intense and reaches beyond the middle of the cells, reaching the brown in iho. 

 proximal end of the fifth posterior cell, thus leaving a well-marked hyaline fenestrate spot 

 in the shape of a parahelogram in the middle of the wing. The brownish tinge in the anal 

 cell and in the anal angle is also more satin-ate than in the female. A slight ])lackish 

 shadow (indistinct in some specimens), is visilde in the hyaline portion of the marginal cell, 

 near the costa (a mere vestige of it is often perceptible in female specimens). 



Hah. A common and wide-spread species. Catskill, N. Y., in July; Waterville, N. H., 

 July (Scudder) ; different parts of British America (the same) ; Lake Superior (A. Agassiz); 

 Yukon River and MacKenzie River (Kennicott) ; Anticosti (Verrill), etc. Twenty-five fe- 

 male and five male specimens. 



Observation. The description was principally drawn from eight well preserved and fresh 

 specimens, male and female, which I caught in the summer of 1874 near the Mountain 

 House, Catskill, N. Y. The specimens from Anticosti are very dark, and the facial pollen is 

 o-ravish, rather than fulvous. I have but little douljt concerning the identity of the above 

 described species with Mr. Walker's C. excUans. Some error must have been committed 

 by him in tlie description of the antennoe, which is not clear. He describes only the female. 



3. Chiysops mitis ii. sp. 



"> Chryso2')s provocans Walker, Dipt. SaumL, ]>. 73. 



?. Apex of the wings hj-nliue ; ]iro.\iiiial half of the two basal cells infuscateil ; anal cell ami anal angle 

 more or less tinged with brownish; two grayish, inlerrnpted lines on the thoi-nx ; abdomen altogether black, 

 with faint triangles of grayish hair. 



Length, 11-12 mm. 



Not unlike the preceding species, from which the female is easily distinguished by an 

 altogether black abdomen, with a grayish and not golden pubescence. 



Female. Head as in C. excitans, only the pollen on face and front is yellowish-gray, in- 

 stead of fulvous ; (in one of iny specimens, however, it is fulvous). Antenna! black, first 

 joint reddish, black at tip ; second, )jlackish-red on the underside. Thoracic doi-sum with 

 two "-ray longitudinal lines, reaching to about the middle ; interval between them brownish, 

 grayish-poUinose anteriorly, where the beginning of a Ijlackish line is visible ; jjleuro) with 

 dense yellowish-gray hairs in the upper part ; some black hairs between the root of the 

 wings and the humeri. Abdomen Ijlack, with a thinly scattered grayish pubescence, more 



