72 REVISION OF THE THYNNID^J OF AUSTRALIA, II., 



b 3 . Labrum not strongly bilobed, usually truncate. 



Aeolothynnus Ashm. 

 ii. Labrum broad and full, scarcely narrowed posteriorly. 



A. Antennae slender at the apex. 



( $ . Pygidium with the truncation broadly ovate; not con- 

 stricted before or on the truncation). Macroihynnus. 



B. Antennae of almost even thickness throughout. 



( 2 • Pygidium constricted before or more rarely on the 

 truncation). Thynnus. 



Key to the Species of Thynnus. 

 g £. i. Labrum strongly narrowed posteriorly. 



A. The joints of the antennae strongly arcuate beneath. 



a. Hypopygium not emarginate. 



a 2 . Hypopygium with an apical spine. 



a 3 . Postscutellum yellow, legs ferruginous. aratus 2 



b 3 . Wholly black. monilicomis Sm. 1 



b 2 . Hypopygium without an apical spine. niticlus Sm. 4 



b. Hypopygium short and emarginate. 



a 2 . Clypeus with a carina. depressus Westw. 5 



b 2 . Clypeus without a carina. fulvopilosus Sm 6 



B. The joints of the antennae not strongly arcuate beneath. 



a. Second recurrent nervure received by the third cubital cell 

 at some distance from the base. 

 a 2 . Abdomen flattened, the segments not constricted. 



a 3 . The three apical joints of the maxillary palpi elongate. 

 a 4 . The second cubital cell shorter than the third on the 

 radial- nervure. 

 a 5 . Hypopygium without an apical spine. 



a 6 . Antennae short and stout. leucostictus 18 



b G . Antennae slender. ada -12 



b 5 . Hypopygium with an apical spine. 



a 6 . Hypopygium with a strong spine on each side 



near the base. agnatus ] 3 



b 6 . Hypopygium with an apical spine only. 

 a 7 . Hypopygium rounded at the apex. 



a 8 . Wholly black; the antennae long and slender. 



longicornis 1 9 



b 8 . The sides of the abdomen spotted with white; 



the antennae rather short. sexmaculatus Sm. 7 



b 7 . Hypopygium truncate at the apex. 



a 8 . Abdomen spotted with yellow on the sides. 

 a 9 . Hypopygium broad, the sides almost 



parallel. trivia/is Sm. 9 



