42 THE entomologist's recoed. 



of the latter in the nests of Formica rufa and Lasms fitliginostis, ih&i 

 some authorities state the number of species to be found with them at 

 from 100 to 150. Of these the actual number of guests does not, per- 

 haps, exceed a third. 



The principal characters of true guests are found in beetles be- 

 longing to the Myrmecophilous Staphylinidae (pL, figs. 1-3), Clari- 

 geridae, Paussidae, Silphidae, Histeridae, &c., to consist of peculiar 

 yellow or reddish-yellow tufts of hair, found on different parts of the 

 body. These prove that the beetles possessing them are licked by 

 their hosts to obtain the pleasant secretion coming therefrom. The 

 presence of a broad short tongue and aborted palpi suggests that those 

 possessing these peculiarities , are fed directly by the host. These 

 adaptive characters, which both point to a genuine hospitable relation- 

 ship, are often to be found in the same species. To these may be 

 added a peculiar formation of the antenna, which denotes a friendly 

 relationship between guest and host, and serves to summon the ant at 

 feeding-time by tapping it with these organs. The Clavigeridac (which 

 form a sub-family distinct from the Pselaphidae) present an excellent 

 example of the combination of these three characters. They are 

 genuine guests, differing from the Psclaplndae in their club-shaped 

 antennae (consisting of fewer segments), the stunted palpi (organs 

 strongly developed in the Psdaphidac), and the shape of the 1st 

 abdominal segment, which is very large, hollow at the base, and 

 covered with tufts of yellow hair on the concave side. The club- 

 shaped antennae serve as organs of communication and allow of friendly 

 intercourse between the beetles and the ants ; the formation of the 

 mouth allows the beetle to be fed by its host, whilst the peculiar form 

 of the 1st abdominal segment and the tufts of yellow hair are closely 

 related with the licking of the beetles by the ants. It is, therefore, 

 quite correct to look upon these three adaptive characters as the real 

 characteristics of the Clavigeridac, and every Claviger must necessarily 

 be an ant guest. This is borne out by the fact that, of the 100 dif- 

 ferent species of this family already described, by far the greater 

 number have been discovered in the society of ants, and of many the 

 actual host is known, especially of the European species and those 

 from Madagascar and North America. 



We find in certain Termitophilous Staphylinidae two adaptive cha- 

 racters, which are a proof of true intercourse, viz. — (1) the broad short 

 tongue and short palpi (in the subfamily Aleocharinae, and only 

 found in the true guests belonging to the Lomechusa group) ; (2) a 

 swelling of the abdomen, in some cases quite abnormal (Physogastry) 

 (pi., fig. 5), and not to be found among Myrmecophilous beetles. 

 The mouth-structure leaves no doubt that these beetles are fed directly 

 by their hosts, whilst the gigantic enlargement of the guest's abdomen 

 is undoubtedly connected with their mode of life, for it also occurs 

 in the Termitophilous ground beetles, Orthogonius Shaumi, and by 

 their larvae, which, when young, are thin and slender, but gradually 

 acquire a long bottle-shaped form under the care of the termites. The 

 yelloAV tufts of hair, as in those of the genuine Myrmecophilous beetles, 

 are not present in the Termitophilous Staphylinidae with thickened 

 abdomen. The tastes of termites evidently differ from those of ants. 

 The Termitophilous beetles have not the club-shaped antennas that 

 facilitate intercourse between the Myrmecophilous beetles and their 



