386 NATURAL HISTORY OF ARTHROPODS. 



Dr. Le Conte says of the beetles of this family : " These are small, shining, usually 

 ovate, sometimes slender insects of a brown color, more or less clothed with erect 

 hairs. They are found various!)' near water, under stones, in ants' nests, and under 

 bark, and are frequently seen flying in the twilight." 



A small portion of the Coleoptera with claviform antennae have the dorsal seg- 

 ments of the abdomen entirely corneous and the elytra very short, not covering the 

 abdomen. Of this portion the Pselaphid^ have the abdomen rigid and the ventral 

 segments five or six in number. The antenna have from one to eleven joints, the 

 labial palpi are very short, the maxillary palpi are usually long and four-jointed, eyes 

 are sometimes absent, claws simple and frequently single, wings often wanting. The 

 species of this family are all very small and many ai'e myrmecophilous, living on 

 friendly terms with ants. As cause for this friendly relationship, it is said that cer- 

 tain species of Pselaphidse secrete, as do the Aphidas, fluids which the ants eat. This 

 kind of life has been so long participated in by these beetles that many species are 

 blind, and are fed, carried about, and protected by the ants exactly as they care for 

 their own larvse ; this is the case with Changer testaceus, a European species which 

 has connate elytra and is apterous. Certain species of this family live in caves, and 

 one of them, Machcerites siibterraneus, is peculiar in having males with eyes and 

 females without these organs. In Articerus, of which several species are found in 

 Australia, the antennae are one-jointed. In the North American genera, Adranes 

 and Fustiger, the antennae have but two joints, and in the former genus, eyes are 

 wanting. 



The Staphylixid^, which, like the Pselaphidae, have short elytra, differ from the 

 latter family in having the abdomen flexible and consisting of eight ventral segments. 

 While including many minute forms, this family also includes some species that are 

 an inch or more in length. The antenna? are generally eleven-jointed, but are variable 

 in form and insertion, the labial palpi are usually three-jointed, the maxillary palpi 

 generally four-jointed. The short truncate elytra usually leave most of the abdomen 

 exposed ; and when these beetles are disturbed, many of them turn the tip of the abdo- 

 men over the body as if intending to sting. Some of them discharge odorous defensive 

 fluids from the tip of the abdomen when they have assumed this threatening position. 

 The wings, when present, can be closely packed away beneath the shoi't elytra. In 

 Pachycorinus dimorphus from New Zealand, Mr. A. Tauvel has noticed that the 

 females are dimorphic, the form that has noiTnal eyes has longer elytra and wings, 

 while the partly-blind form has very short elytra and no wings — a curious correlation 

 of locomotion and sight. Some species of Staphylinidae have, in addition to the com- 

 pound eyes, a pair of ocelli. 



The larvae of Staphylinidas resemble the imagos more than is usual 



with Coleopterous larvae, chiefly on account of the larval-like appearance 



of the imagos themselves. The antennse are always four-jointed, 



although apparently five-jointed in some genera. The mouth-parts 



are well developed, the maxillary palpi are of three or four joints, the 



ocelli vary according to genera from one to six on each side, the body 



is elongate and is usually ai-med at the anal end with a pair of append- 



^'Voc^mJ!""' ^ges which are mostly two-jointed. These agile larvae are of a firm 



texture, of a brownish black or yellowish color, and they pupate, for 



the most part, underground or beneath rubbish on the ground. In many forms the 



metamorphosis lasts but one year. 



