ART. 19 AMERICAN MUSCOID FLIES — ALDRICH 17 



discal bristles located at the front edjie and another pair e(iiially 

 large of marginals at the hind edge; the third segment has no dis- 

 cals, a peculiar fact when they are so well developed on the second. 

 In the type of serlcea there are evident scars of the large discals on 

 the front edge of the second segment and also a pair of marginals at 

 the liind edge, the third segment having no scars of discals. 



Brauer and Bergenstamm as well as Van der Wiilp were in error 

 in overlooking the scars on the second segment. The principal dif- 

 ference between the two specimens is in the paiafrontals, which in 

 the male are so broad that they reduce the frontal stripe to a mere 

 groove in its narrowest part before the ocelli. The female has broad 

 and conspicuous parafrontals, but the frontal stripe still retains at 

 the narrowest a width of nearly one-half of one parafrontal. 



Female. — Front 0.31 of head width at the vertex, slightly wider 

 at the antennae, the face becoming narrower again at the lower edge 

 of the eyes. Frontal bristles about six, barely reaching the base of 

 the antennae. Two proclinate orbitals, ocellars minute, diverging 

 ■forward. Parafrontals silvery except on the upper part, the same 

 smooth shining surface extending down the parafacial and across 

 the face. The transverse impression is very narrow, extending from 

 the vibrissa backward under the eye. In profile the head is hemi- 

 spherical ; the eye occupies all but a narrow rim of this figure. Back 

 of the head flat and the cheek only about one-tenth of the eye 

 height. The lateral edge of the mouth is black in ground color, in 

 a narroAv triangle extending hardly to the vibrissa and bearing 

 three bristles behind it which are at the oral margin ; face flat, with 

 bare ridges. Antennae yellow as far as arista, the remainder infus- 

 cated; third joint more than twice the second, slender, but a little 

 swollen at tip, the arista w^ith delicate plumosity ; palpi yellow, rather 

 small; proboscis decidedly small but with large yellow labella. 

 Lunule unusually prominent, yellow, contrasting with the dark 

 brown frontal stripe Thorax black in ground color except the 

 humeri, postalar calli, and the margin of the scutellum. Mesonotum 

 covered with golden pollen, wliich is quite thin in the middle region, 

 more distinct on the sides, front, and hind edges and scutellum. 

 Pleurae silvery-pollinose from the notopleural suture on all but the 

 posterior part. Chaetotaxy: Acrostichal 3, 3(?) ; dorsocentral 3, 3; 

 humeral 2; posthumeral 1; intraalar 2; supraalar 2 (posterior 

 small); postalar 2; presutural 1: notopleural 2; scutellum with two 

 lateral pairs and a good-sized decussate apical pair, no discals; 

 st^rnopleural 1, 1; postscutellum well developed. Calypters pale 

 yelloAv, the hind ones large, with rim and fringe of same color. 



Abdomen shining yellow without pollen, the tip shining black 

 including the last third of the third segment and all of the fourth 



6642—29 .3 



