312 NATURAL HISTORY. 



of our illustration is a continental European species, differing from our common Gyrinus by its more 



striated and less polished surface. 



The family Paussidse, which we have thought convenient to notice in this place, is one of those 

 anomalous forms, numerous in the Coleoptera, whose position in any system is very un- 

 certain. Some of their species are known to be tenants of the nests of Ants, 

 and to be tended with care and jealousy by those insects ; but nothing is 

 known of the habits of the great majority, most of which are rare, and 

 met with only in houses at night in tropical and warm countries, whither 

 they are attracted by the lights burning in the rooms. If they are 

 habitually guests of Ants, guarded and fed by them in the recesses of their 

 nests, some of the anomalies in their structure might be accounted for, on 

 EN-HYURXJS t^ ground of the natural variations in the various parts of their struc- GYR1XUS DIS ~ 



SULCATUS. . TINCTUS. 



tore not having been controlled by natural selection in the free struggle 



for existence. Granted this, it would be easy to believe they are strongly-modified forms of 

 Carabidae, allied to the sub-family Ozcenince, as Burmeister believed them to be. 



The Paussidce are oblong insects of small size, distinguished at first sight from ordinary Beetles 

 by the extraordinary form of their antennae. These organs run into all sorts of fantastic shapes in 

 the different species ; but inordinate width and bulk, and the tendency to a bulbous form in the ter- 

 minal joint, are the most general characters. The number of tarsal joints is normally five ; when there 

 are only four, it is in consequence of the small basal joint becoming inconspicuous or wanting; in other 

 respects the legs, as well as the form and proportions of head, thorax, and body, are not essentially 

 different from the same parts in many Adephaga. A peculiarity of the elytra the existence of a small 

 fold and breach of continuity in the lateral margin, near the apex is very significant from the point of 

 view of a relationship to the Carabidce, as this curious feature is known to exist nowhere else in the 

 Coleoptera save in the group Ozceninae belonging to that family. Their faculty of crepitation also speaks 

 for the same relationship, for the Ozseninae, as well as the Artillery-beetles, possess this rare property. 

 Against all this, however, stands the widely-different position of the mouth, and the structure of its 

 different parts. The mouth, instead of being at the anterior extremity of the head, as in the 

 Adephaga, is on the under side; but passing by this, as probably caused by the bulky antenna) 

 necessitating the strengthening of the forehead, it must be allowed that the totally different form and 

 nature of the mentum, or chin, goes quite against any near relationship to any of the Adephaga; 

 for the definite form and structure, and the size of this organ, are quite essential characters of the 

 tribe. In the Paussidse it never approaches the Adephagous form, but is a narrow transverse plate, 

 often indistinct, and the lower lip, which in Adephaga is subordinate to the mentum, is here of 

 greater relative development. The maxillae, too, are destitute of articulated outer lobe ; but these 

 members are so eccentric in shape in the family that not much reliance can be placed on this point. 



More than one hundred species of these grotesque Beetles are known, chiefly from the tro- 

 pical regions of Asia and Africa ; but one (Paussus favieri) is found in South- western Europe. Some 

 collectors in South Africa and in Australia have been able to secure a large number of some of the 

 species by assiduous search in Ants' nests. With regard to their social relations to the Ants, less is 

 known ; but it appears that some kinds are really enforced guests of the Ants. Mr. Ayres, of 

 Potchefstroom, declares this to be the case with regard to the Pentaplatarthus pausso'ides. He found a 

 large number of the insects by digging in the nests of an active species of Formica in the Transvaal, 

 and observed the Ants dragging the Beetles into their galleries, further stating that they bring them 

 out when the sun is shining, and pull them in again when clouds begin to appear. Other observers 

 have noticed that the Paussi are not willingly guests of the Ants, but are forcibly seized and 

 detained by them. A common Australian species is found under dried cow-dung ; and Paussi are often 

 found in South Africa under stones. 



TRIBE PALPICORNIA. 



The tribe Palpicornia have for their chief point of distinction among the Coleoptera the great 

 length and slenderness of their palpi, which are longer and more conspicuous than the antennae : these 

 latter being short, of from six to nine joints only, the terminal ones thickened into a club. The 

 maxillae and their exterior lobes are unarmed. The typical genera of the tribe are aquatic, and have 



