by the presence of a median constriction evidence of the fusion of 

 two segments, 3rd-6th small and sub-moniliform, the terminal 7th 

 large and conical, bearing a few scattered bristles and longer than 

 the sum of the three preceding. Maxillary palpi simple and two- 

 jointed, bearing several fine scattered hairs, basal joint large, bulbous, 

 apical smaller and somewhat falcate* Mesonotum large, the anterior 

 margin arched and overhanging the head, scutellum sub-elliptical, post- 

 scutellum large. Abdomen 8-segmented, narrow and elongate. Hypo- 

 pygium forcipiform, bearing a pair of falcate, two-pointed claspers. 



Hab. Types $ and 9 Nahikn, Maui (400-800 ft.) also 

 Lahaina, Maui (1000 ft.); Kohala, Hawaii (1200-1500 ft.) 

 Terry coll. 



In rapid streams and water-falls. 

 This species is a decidedly characteristic inhabitant of certain 

 mountain streams in Maui and Hawaii. The black-winged, ac- 

 tive adults continually dancing over the rushing water, fre- 



*This organ appears to be very plastic, exhibiting considerable 

 variation of form, regardless of sex; one specimen examined pos- 

 sessing a single-jointed left palp, the right being normal. 



Legs long and slender (anterior pair used in walking) ; tarsi five- 

 jointed and cylindrical. Anterior: 1st tarsal joint nearly three times 

 as long as 2nd, which is equal to the sum of 3rd and 4th. Median: 

 1st tarsal joint nearly three times as long as 2nd, which is hardly 

 equal to the sum of 3rd and 4th. Posterior: 1st tarsal joint rather 

 more than twice as long as 2nd, which is equal to the sum of the 3rd, 

 4th and 5th. Claws well developed and simple in both sexes, empodia 

 large and pectinately plumose; pulvilli absent. Median and lateral 

 lobes of apical tarsal joint large. 



Wings large, reaching a little beyond the apex of abdomen, mem- 

 brane somewhat coriaceous, posterior margin parallel with the costal, 

 costa bearing numerous minute hairs; anal angle rectangular, mid- 

 cross-vein arising slightly before the middle, auxiliary becoming ob- 

 solescent just before reaching the costa; 1st longitudinal bearing a 

 few scattered hairs, and extending beyond the middle of the costa, 

 forming an acute-angle at point of junctures; 2nd longitudinal absent; 

 3rd and 4th longitudinal united by oblique mid-cross-vein; furcation of 

 5th longitudinal before middle and forming an acute angle, the lower 

 branch curved; 6th longitudinal well defined becoming obsolescent 

 just before reaching the wing margin; anal angle rectangular. 



9 Very similar to the male, with the following differences: Legs 

 shorter, the tarsal ratio however is the same; wings not extending 

 beyond the apex of abdomen; the abdomen stout, parallel-sided, pos- 

 terior extremity pointed, the terminal (8th segment) triangular in 

 dorsal aspect, apically pointed, and bearing laterally a pair of flat- 

 tened appendages. The ventral terminal segment is also triangular 

 and also bears a pair of small flattened appendages. 



