164 THYNNID.E. 



16. Thynnus aterrimus. 



Male. Length 6 lines. — Black ; shorter and broader than is usual 

 in Thynnideous insects. The face and body beneath with cinereous 

 pubescence ; the prothorax with the anterior margin very narrowly 

 yellow ; the postscutellum and a very narrow line continued to the 

 posterior wings yellowish ; wings f us co-hyaline, the nervures black. 

 The head and thorax very closely punctured. Abdomen shining, 

 and having very shallow distant punctures ; the segments deeply 

 constricted ; the terminal ventral segment tridentate. 



Hal. Swan River. 



17. Thynnus perplexus. 



Male. Length 6 lines. — Black ; the head and thorax with yellow 

 markings, the abdomen with interrupted yellow fasciae on each 

 segment; the legs ferruginous. The mandibles, the clypeus, a 

 spot above each antenna, and two minute spots on the vertex, 

 yellow. The posterior margin of the prothorax, the tegulse, an 

 ovate spot on the mesothorax, and also one on the scutellum, 

 yellow ; the femora and thorax beneath with white pubescence, as 

 well as the sides of the metathorax ; wings hyaline, the nervures 

 ferruginous. Abdomen with six interrupted yellow fasciae, the 

 seventh segment ferruginous, the inferior plate forming a tri- 

 angular appendage ; beneath ferruginous : the margins of the seg- 

 ments black ; the second and three following segments with two 

 large ovate maculae. 



Female. Length 5 lines. — Head, thorax, and legs ferruginous ; the 

 head wider than the thorax, and with a few scattered punctures. 

 Abdomen black above and ferruginous below ; the basal segment 

 yellow above, black at the extreme base, and with a narrow black line 

 in the middle ; the second segment transversely striated, and with a 

 large lateral subquadrate spot ; the three following segments with 

 very broad yellow fasciae, slightly interrupted in the middle. 



Hah. Swan River. 



18. Thynnus petulans. 



Male. Length 9 lines. — Head and thorax closely punctured and 

 black ; abdomen, tibiae, and tarsi ferruginous. The mandibles 

 reddish yellow, their apex and inner margin rufo-piceous ; the 

 clypeus truncate, its margin yellow, and emitting upwards a 

 yellow triangular mark in the middle. The posterior margin 

 of the prothorax and the tegulse ferruginous; the metathorax 

 with white woolly pubescence; wings pale fulvo-hyaline, the 

 nervures dark ferruginous; beneath with white pubescence, the 

 legs fringed with the same. Abdomen with the extreme base 



