THYNXUS. 165 



black ; the apical margins of the segments slightly constricted and 

 more or less fuscous in the middle, where the fuscous colour widens 

 into a triangular shape ; beneath, the segments are black laterally 

 and ferruginous in the middle; the apical segment above lon- 

 gitudinally striated, the ventral segment triangular, its margins 

 black. 



Hab. Swan River. 



19. Thynnus nigropectus. 



Male. Length 8 lines. — Yellow, with black markings ; the head 

 above the antennas, the latter, and the tips of the mandibles black ; 

 between the antennae is a yellow triangular-shaped spot that runs 

 up to the anterior ocellus ; a yellow line above the antennae at the 

 inner margin of the eyes, not extending to their summit. A 

 transverse line in the middle of the prothorax, the mesothorax, 

 the base of the scutellum, and the pectus, black; two abbre- 

 viated lines, and also a line over the tegulae, yeUow ; the tarsi 

 black; the wings hyaline, with the nervures black. Abdomen 

 truncate at the base, the apical margins of the first and second 

 segments black; the following segments black, with a broad 

 yellow fascia on the third, fourth, and fifth, interrupted in the 

 middle ; the sixth has a lateral yellow spot ; the apical segment 

 truncate above, and with longitudinal irregular striae, beneath the 

 produced truncated portion it is smooth and shining, and has la- 

 terally two short acute spines ; the apical ventral plate trifid ; the 

 basal margin of the ventral segments narrowly black. 



Hab. Swan Eiver. 



20. Thynnus vespoides. 



Male. Length 8 J lines. — Black ; the abdomen with yellow fasciae, 

 the tibiae and tarsi ferruginous. The clypeus truncate, and, as 

 well as the mandibles, yellow, the latter black at their tips ; the 

 cheeks and inner margin of the eyes with white pubescence. 

 Thorax closely punctured; the metathorax densely clothed with 

 long white pubescence, on the sides and beneath it is shorter and 

 less dense; the femora fringed with the same beneath; wings 

 faintly fulvo-hyaline, the nervures black. Abdomen truncate at 

 the base ; the first, second, third, and fourth segments with the 

 margins narrowly black ; the segments pale yellow, and with a 

 small ovate black spot laterally ; the fifth segment with a narrow 

 pale yellow fascia, interrupted laterally in a line with the black 

 spots ; the sixth and seventh segments black ; the apex produced 

 in the lower plate into a trifid appendage. 



Hab. South Australia. 



