PROC. ENT. SOC. WASH., VOL. 23, NO. 9, DEC., 1921 197 



abdominal appendages are by no means all but invisible vestiges, but are fully 

 one-half as long as the large first segments of the first pair of appendages. 



Acerentomon americanum, n. sp. 



Species medium-sized, uniformly yellowish. Head long, pointed and almost 

 completely concealing the prothorax from above; pseudoculi lateral, pit-like; 

 rostrum conspicuous. Dorsal part of prothorax about three times as broad as 

 long. Mesothorax slightly smaller than metathorax and both with convergent 

 sides. Abdomen long, unicolored; segment seven larger than eight, slightly 

 swollen at the level of tergal apodeme, the latter with a stout posterior horn 

 which reaches the pleuron and a more slender anterior horn which does not reach 

 the pleuron, tergal plate with a single transverse line. Legs rather stout; 

 anterior pair extending beyond the tip of rostrum by three-fourths the length 

 of their tarsi; tarsi of anterior legs each ending in a long, slightly curved claw. 

 Length when much extended, 1.17 mm.; width, 0.14 mm. 



Type. Cat. No. 24,582 U. S. N. M. 



Described from the type specimen, a female collected in decay- 

 ing leaves at Takoma Park, Maryland. This species differs from 

 doderoi and microrhinus in several minor details and markedly 

 in the shape of the rostrum and of the tergal apodemes, especially 

 the seventh tergal apodeme. Only a single specimen of this 

 species has been obtained. 



Acerentomon conurus, n. sp. 



Species undersized for its genus, pale yellow and almost uniform in coloration. 

 Head very long, being over twice as long as broad; pseudoculi pit-like, lateral; 

 rostrum very small and short. Prothorax about as broad as mesothorax and 

 mostly concealed above by the superplaced head. Meso-, and metathorax 

 about equal, the latter slightly the broader. Abdomen with sides almost 

 parallel from the base to the end of segment six; segment seven a truncate cone, 

 as is eight; apodeme of seventh tergal plate twice forked laterally and squarishly 

 thickened near its middle; eighth abdominal segment with transversely striated 

 band. Anterior legs extending beyond the tip of rostrum by the full length 

 of the tarsi; the latter armed with claws that are longer, stouter and less curved 

 than those on the other legs. Length with segments neither extended nor 

 telescoped, 0.81 mm.; width, 0.12 mm. 



Type Cat. No. 24,583 U. S. N. M. 



Described from the type only, a female taken at Takoma Park, 

 Maryland, from decaying leaves. This species is considerably 

 smaller than the others found in the genus and is at once sepa- 

 rated by the peculiar shape of the seventh abdominal segment. 

 An examination of the mouth-parts shows the maxillary palpi 

 to be three-segmented, instead of four. The reason for the 

 apparent discrepancy between the number of segments in this 

 pair of appendages in this species and the number apparently 

 found in others will be found only by further investigation. The 

 species is abundant in moist decaying leaves at Takoma Park. 



