74 PROCEEDINGS OF THE NATIONAL MUSEUM VOL, 97 
fourth where they separate enough to allow the slender, pointed 
dorsally directed apex of the median lobe to fit between their tips in 
a socket formed by ventrally directed teeth, one on the internal ventral 
margin of the tip of each of the lateral lobes; median lobe flared ventro- 
basally to nearly the combined widths of the lateral lobes, tapering 
quickly apically to very slender tip, dorsally curved; median lobe 
sclerotized ‘only laterally and dorsally, except for small rectangular 
piece imbedded separately in its ventrobasal membranous area. 
Type and paratype.—U.S.N.M. No. 57322. 
Distribution.—Cornpuss Gap, July 25, 1941, type male and one 
paratype male, latter from spider’s web. 
Named for Prof. S. O. Mast, of Johns Hopkins University. 
Genus MICRODIPHOT Barber 
This genus was erected by Barber originally to accommodate M. 
cavernarum Barber, a form apparently closely allied to Diphotus in 
aedeagal structure and position of photogenic organs, but differing in 
its minute size, its laterally compressed cylindrical shape, its sinuate 
elytra, and its pronotum bluntly arcuate in both anterior and poste- 
rior margins. M. barberi, described below, agrees with the genotype 
in all the mentioned particulars, thus strengthening the generic segre- 
gation of these forms. In addition, as described later, M. barber has 
a flat frons, and a tibial spur pattern different from all other Jamaican 
lampyrid genera, agreeing in both these respects also with M. caver- 
narum. . 
MICRODIPHOT BARBERI, new species 
PuatE 1, Figure 8; PuatE 2, Fiaurss 18, 19; Puate 3, Figure 24 
Field characters —Dimensions ranging from 4.6 by 1.0 to 5.3 by 1.1 
mm. Body very slender and nearly cylindrical; elytra and most of 
abdomen black; pronotum widest at middle and arcuate both in front 
and hind margins, yellow to pink. 
Male.—Pronotum 0.9 by 0.9 mm.; nearly flat; widest at middle, 
tapering equally to front and rear and resembling that of Microdiphot 
cavernarum Barber; apical and basal margins bluntly arcuate, hind 
angles obtuse; predominantly glistening yellow with irregular pinkish 
mottling, apical sixth dark brown; narrow deep groove with a prom- 
inent row of small indentations close to lateral and apical margins; 
narrow median sagittal groove to apical fifth. Scutellum flat, elongate, 
rectangular, light yellow, and sometimes with shallow median sagittal 
groove. Mesonotal plates white with dark brown borders. Elytron 
3.7 to 4.3 mm. long; black or very dark brown, with narrow, white 
lateral and sutural borders; widest at humerus (0.5 mm.), tapering 
to 0.4 to 0.45 at basal fourth, then parallel-sided to apical fifth where 
final taper begins, mainly in lateral margin; elytra slightly sinuate so 
