5i)4 



MK. R. K, 'I'UKNEK ON 



The present paper is fouDfled on the collection of the British 

 Musemn, Avhich contains nearly all the described Australian 

 species, to which I am able to give a key, but owing to numerous 

 gaps in the collection from other regions, I cannot give a key to 

 the whole genus, but only to the species from certain regions. 

 The sexual differences are not usually great, consisting of a dif- 

 fei-ence in the shape of the anterior margin of the clypeus, and 

 usually in an increase in tlie distance between the eyes in the 

 male. But several species, such as insigve Sickm., regalis Sm., 

 tuherculatus Sm., and mdijjennis Sm,, have carinas or tubercles 

 on the ventral segments of the male, and algirictim Kohl and 

 fenesiratus Sm. show a dilatation of some of the joints of the 

 flagellum in the male. 



The species which I have not seen are indicated by an 

 asterisk. 



Kei/ to the Ethiopian Species o/Pison (including those fiom 

 St. Helena, Mascarene, and Seychelles Islands). 



1. Two cubital cells (Pisonoides) 2. 



Three cnhital cells, very rarely with only two on one 



side (Fison) 3. 



2. Legs, except the 'coxaj, ferrnginous 5 tii-st recurrent 



nervure interstitial with the tirst transverse cubital [(Seychelles.) 



nervnre T. isola tutn Turn. 



Tarsi and fore tibise testaceous, the rest of tlie legs 

 almost entirely black ; first recuiTent nervure re- 

 ceived before the apex of the first cubital cell _P, testaceipes Turn. 



3. Second recurrent nervure received close to the middle 



of the second cubital cell P. argentatus Shuck. 



Second recurrent nervure received near the apex of [(Mauritius.) 



the second cubital cell or interstitial with the 

 second transverse cubital nervure 4. 



4. The whole dorsal surface of the median segment 



obliquely striated 5. 



Dorsal surface of the median segment at most with a 



few oblique stnse at tTie base 6. 



5. Striae of median segment strong ; the male with the 



apical abdominal segments ferruginous red P. xnnthopus BruU^. 



Stria? of median segment very close and delicate; 



abdomen entirely black P. denticeps Cam. 



6. Sides of the median segment (niesopleurae) strongly 



obliquely striated P. cJypeatus Cam. 



Sides of the median segment punctured or smooth, 



at most with a few delicate strise at tbe base 7. 



7. Median segment smooth and shining, except in the [(Seychelles.) 



median sulcus and on the posterior slope P. spec^ilare Turn. 



Median segment mon; or less strongly punctured ... 8. 



8. Sides of median segment delicately striated at the 



base P. transvaalensis Cam. 



Sides of median segment punctured 9. 



9. Abdomen smooth and shining, with onlj^ microscopic 



punctures; median segment very coarsely rugoselj^ [(St. Helena.) 



punctured P. ivoliasfoni Turn. 



Abdomen closely and distinctly punctured, more 



strongly on the basal than on the apical segments ; 



median segment less coarsely punctured 10. 



10. Second cubital cell minute, or even obsolete on one 



side P. incrqiiale Turn. 



Second cubital cell normal 11. 



