2 PROCEEDINGS OF THE NATIONAL MUSEUM vol.79 



2. Proboscis distinctly exceeding the height of head, the apical 

 joint very slender, tapering from base to tip ; labella leathery, 



hardly wider than proboscis Siphosturmia Coquillett 



Proboscis not longer than the height of head, the apical joint 

 moderately stout and uniform in thickness from base to 

 tip; labella soft or fleshy and distinctly wider than pro- 

 boscis Siphosturmiopsis Townsend 



Genus MICROSILLUS Aldrich 



Microsillus Axdkich, Proc. U. S. Nat. Mus., vol. 69, art. 22, p. 20, 1926. Female 

 only; type, Houghia haccharis Reinhard. 



The description of H. haccha7^s ^ was based on a single female 

 specimen from Texas, and hitherto the male has been unknown. 

 The accumulation of four additional specimens, including the male 

 sex, makes it possible to add a number of essential items. The 

 genus was described in the form of a comparison with SiphosturTnia 

 to which it is related. The resemblance, however, is confined largely 

 to the female, and the male shows a number of striking and im- 

 portant differences. With these discoveries it appears desirable to 

 redescribe the genus fully and to amend the specific characterization 

 of the type species from the additional material now at hand. 



Generic characters (from the type species). — Face in profile very 

 flat and concave below, with the mouth jutting forward between 

 the vibrissae; the latter on level with oral margin. Occiput on 

 lower part bulging backward, so that the lower edge of the head is 

 long, rather straight, and about equal to the axis at antennae. 

 Proboscis when fully extended not much exceeding the height of 

 head; palpi present. Front rather broad in both sexes, with or- 

 bitals, ocellars, and both pairs of verticals well developed. Frontals 

 about six, diverging toward the eye below antennae, the uppermost 

 two in each row rather stout and reclinate. Antennae in both sexes 

 almost reaching the oral margin, second joint about one-fourth the 

 length of third ; arista hardly as long as antennae, penultimate joint 

 only slightly longer than wide. Sides of face narrowed below, 

 bare. Cheeks flattened, about one-fourth the eye height. Eyes 

 bare. 



Thoracic chaetotaxy : Acrostichal, 3, 3; dorsocentral, 3, 4; humeral, 

 4; posthumeral, 2; presutural, 2; notopleural, 2; intraalar, 3; su- 

 praalar, 3; postalar, 2; pteropleural, 1 (small); sternopleural, 2, 2; 

 scutellum with one discal, three lateral, and a smaller decussate ap- 

 ical pair. Postscutellum normal ; postnotum at side beneath calypter 

 bare. 



Abdomen varying with sex, in female the fourth segment some- 

 what elongate, noticeably deflexed, and tapering to a rather sharp 



1 Ann. Ent. Soc. Amer., vol. 14, p. 332, flga. 5, 6, 1921. 



