374 



slender, fused nearly to their apices ; body tapering posteriorly, the 

 segments very distinct, no distinguishable hairs present ; posterior 

 pseudopods much elongated, divergent, their apices armed with two 

 circles of long, slender, pale claws, the preapical row rather stouter 

 than the apical one ; dorsal respiratory organs long and slender, rather 

 pointed, the two hairs just above their bases distinct ; anal tuft with 

 six sensory hairs, the basal papilla long and slender, about five times 

 as long as thick. 



Pupa. — Length, 2.25 mm. Thoracic respiratory organ large, in 

 the form of a cornucopia (PI. XXIV, Fig. 14) ; a transverse row of 

 small pointed tubercles between the respiratory organs; apical abdom- 

 inal appendages as in Figure 8, Plate XXVI. 



The larva described, was taken from the Illinois River, with a 

 Birge net, August 27, 1894; and the two pupae were taken amongst 

 vegetation at the same place (Havana) and by the same method, 

 August 25, 1894. 



6. Tanypus marginellus, n. sp. 



Male. — Yellowish or greenish, slightly shining. Scape of anten- 

 nae blackish, flagellum obscurely greenish. Mesonotum with three 

 black vittae. the middle vitta divided by a narrow yellowish line, the 

 spaces between vittae with gray pruinescence ; pleurae blackish gray 

 with the exception of the membranous portions, which are yellowish 

 or greenish; scutellum yellow darkened at base; postnotum shining 

 black. Abdomen shining; basal two-thirds of each segment black; 

 hypopygium yellowish. Legs yellow, without distinct dark marks. 

 Wings clear, veins yellow, cross vein not infuscated. Halteres yellow. 

 Hairs on body and legs yellow, plumes of antennae brown. 



Antenna distinctly longer than head and thorax together. Prono- 

 tum distinct to upper margin. Thoracic hairs rather weak. Abdomen 

 slender, surface hairs regularly distributed; hypopygium as in Figure 

 10, Plate XXVII. Legs slender, femora and tibiae of mid and hind 

 pairs rather long-haired ; fore tarsi pubescent, basal joint slightly less 

 than two thirds as long as tibia. Third vein not extending to apex of 

 wing; cross vein a little more than one third of the distance from 

 humeral vein to wing-tip. 



Female. — Similar to male except that the abdomen is almost uni- 

 colorous yellow, the antennae are shorter than the head and thorax 

 and short-haired, and the cell enclosed by the third vein disappears 

 before apex of costa. 



