6 Descriptive Catalogue [1897. 



three kinds of Paussus which I kept in captivity. "While in the act 

 of taking food the labial palpi hang at right angles with the 

 mouth, and no movement of the jaws is visible ; in fact it was only 

 by using a very shallow formicarium that I was able to watch the 

 Paiissi taking food. 



It is difficult to detect the sexes of Paussidce from external 

 characters, and, with a few exceptions, dissection is the only means 

 available. I have already stated that the males seize hold of the 

 prothoracic cavity of the female with their jaws for mating, but this 

 prothoracic cavity is common to both sexes in Paussus, and there are 

 other genera where this prothoracic cavity is wanting, but in those 

 all the tarsi are dilated and covered underneath with dense, short 

 papillae. It is well known that many male Carabiclce and Hydrophiliclce 

 have the front, and sometimes the intermediate, tarsi provided with 

 such cusp-like development in order to maintain the female for 

 mating purpose, but in Gerapterus these papillae occur in both sexes ; 

 of that there can be no doubt — I have proved it by dissection. It 

 is, however, possible to recognise the female by means of the slight 

 acumination of the median part of the apex of the pygidium. I 

 have not yet met with the female of Arthropterus , but Baffray states 

 that in this sex the tarsi are ciliate underneath, and it yet remains 

 to be seen if in Pleuropterus , the other South African genus having 

 no excavated prothorax, the tarsi of the female are papillose under- 

 neath. In Paussus Gurtisi the antennal club is a little longer in the 

 male than in the female, but in P. planicollis, an Abyssinian 

 species, it is longer in the female than in the male. 



When touched either by the hand or with a straw the Paussidce 

 crepitate, and the detonation is accompanied by the discharge of a 

 caustic fluid which not only stains the finger as iodine or lunar 

 caustic would, but the whole body of the insect as well as its 

 immediate neighbourhood is covered with a bright yellow fluid, 

 which becomes pulverulent almost immediately, and slowly dis- 

 appears. Free iodine is reported to have been found in the discharge 

 of a Javanese species, Gerapterus quadrimaculatus . 



I am rather inclined to think that the detonation is produced by 

 the contact of the fluicl with the air, because, although expelled from 

 behind, the anterior part of the animal is immediately covered by the 

 yellow pulverulence, and is, therefore, in the centre of the explosion. 



Raffray, in his ' Eecherches anatomiques sur le Pentaplatarthrus 

 paussoides,' has given a masterly account of the secreting and 

 detonating organs of this Paussid. He finds that the organ for the 

 secretion of the caustic fluid is really a duplicate one, one on each 

 side of the body, independent from one another, and situated far 



