FOSSORIAL WASPS. 593 



Genus PisoN Jur, 



All/son Spinola, Ins. Ligiu-. ii. 4, p. 253 (1808) (nee Jurine). 



Pison (Jurine) Spinola, Ins. Ligur. ii. 4, p. 255 (1808). 



Tachybzdus Latr. Gen. Crust, et Ins. iv. p. 75 (1809). 



Neinhridia Brulle, Ann. Soc. Ent. France, ii. p. 408 (1833). 



Pisonitus Shuck. Ti-ans. Ent. Soc. London, ii. p. 79 (1837). 



Pisonoides Sni. Journ. Proc. Linn. Soc, Zool. ii. p. 104 (1857) 

 (subgenus). 



Parapison Sm. Trans. Ent. Soc. London, p. 298 (1869) {=Pi- 

 sonoides). 



Psettdonysson Rad. Horse Soc. Ent. Ross. xii. p. 104 (1876). 

 ^^aracermivius Rad. Horse Soc. Ent. Ross. xxi. p. 432 (1887) 

 ( = Pisonoides). 



Taranga W. F. Kirby. Trans. Ent. Soc. London, p. 201 

 (1884). 



Pisum Schulz, Spolia Hymen, p. 212 (1906). 



The genus is very widely distributed, being found in almost 

 all tropical and warm temperate countries, though it does not 

 extend into the northern portions of the temperate zone. But 

 the number of species in the different portions of its range is 

 most uneven : out of one hundred and nine species catalogued fifty 

 are from Australia, seventeen from the Austro-Malayan and 

 various itisular regions, thirteen from the Oriental, nine from the 

 Palfearctic, nine from the Ethiopian, and eleven from the Ameri- 

 can regions. In my opinion, this distribution points to the 

 genus being in a declining state, the majority of the species 

 being from Australia or from island areas where the competition 

 is likely to be less keen ; the number of species on the large 

 continental areas is not great, noj" are individuals particularly 

 numerous. Such of the species as have been observed build mud 

 nests in holes in wood, key-holes, or similar situations, stocking 

 their nests with small spiders, which are paralysed by stinging. 

 Owing to these habits the species are easily transported on ships, 

 giving rise to a considerable extension of range in several species, 

 such as P. spinolce and P. argentatus. 



The genus has been divided into subgenera according to the 

 neuration, but these subgenera are in no way natural ; Pisonoides 

 Sm., which must replace the later and more generally used 

 Parapison Sm., has the second cell absent, but the species are 

 not all nearly related to each other, and I have seen specimens 

 of Pison in which the second cubital cell is absent on one side 

 and present, though of small size, on the other side. Pisonitus 

 Shuck., which is distinguished by the reception of the second 

 recurrent nervure close to the middle of the second cubital cell, 

 is difficult to separate with einj certainty owing to variation in 

 the position of this nervure in some species of Pison, as in 

 P, xanthopus Brulle. The size of the second cubital cell is 

 subject. to much variation in many species oi Pison and cannot 

 be relied on for specific distinctions. 



