PSYCHODA. 219 



16- jointed ;* the two basal or scapal joints differentiated, short 

 and broad ; the flagellar joints varying in shape according to the 

 species, usually oval, cylindrical or flask-like, each with a quantity 

 of verticillate hairs forming a cup- or basin-like corolla. All the 

 organs of the head difficult of observation without dissection owing 

 to the dense pubescence of the whole head, except the eyes. 

 Thorax robust, considerably arched, barely longer than broad ; 

 surface smooth, but densely covered on all sides with thick long 

 bristly hairs. . Scutellum very small, wholly inconspicuous, meta- 

 notum arched, both covered with dense pubescence. Abdomen 

 short, broad and thick, barely longer than the thorax ; arched, 

 equally densely pubescent as the thorax, with similar thick bristly 

 hairs ; segments somewhat compressed. The male genitalia consist 

 of two pairs of appendages, the lower pair being united to a 

 ventral plate, which latter really represents the ultimate abdominal 

 segment, Viewed from the side, this plate, which is always very 

 conspicuous, appears like the basal joint of the lower appendages, 

 but these latter consist of only a single joint, usually of con- 

 siderable size, elongate-conical, slightly curved, pointing upwards, 

 bearing at the tip at least one chitinous spinule. The upper 

 appendages are smaller than the lower pair, two-jointed, the basal 

 joint being the shorter, the second one tapering to a point, but 

 without a spinule. No chitinous intromittent organ apparent, 

 according to most authors, but Mr. Leonard Haseman, writing on 

 the North American species, mentions having observed it in one 

 or two species. In the female the genital apparatus consists of a 

 horny, upwardly curved, pointed ovipositor, constructed of two 

 laterally compressed valves closely applied to one another. Leys 

 short, robust, subcylindrical ; tibise generally rather longer than 

 the femora, metatarsus much longer than any other tarsal joint, 

 last tarsal joint small. Legs generally covered with small scales, 

 with some long bristly hairs on the femora and tibise ; tibiae and 

 tarsi often with an apical circlet or band of scales of a different 

 colour (white or yellowish). Wings very broad and comparatively 

 very large, although in some species narrower, even lanceolate ; 

 always covered thickly with hairs, which may cover the wing-mem- 

 brane as well as the veins (in which case the hairs are generally of 

 a rather finer texture). In other species the hairs are confined to 

 the veins, and are more bristly in nature, often scale-like, and 

 always arranged in two divaricate depressed rows, lying practically 

 flat on the wing-surface, the hairs being of sufficient length to lie 

 across those of the two immediately adjacent veins. f Erect, long, 



* Some authors, Mr. Leonard Haseman for instance, speak of some species 

 having 17-jointed antenna; ; but it is probable that the so-called seventeenth 

 joint is only formed by the constriction of the sixteenth. 



t No previous author appears to have noticed this radical difference in the 

 distribution of the hairs on the wings, yet though I overlooked its importance 

 in my first notes on this family, a more serious examination of the species 

 resolved them easily into two groups on this character alone. The species 

 of Pericoma are amenable to the same division. 



