TEE BRACHELYTRA. 



315 



TRIBE BRACHELYTRA. FAMILY STAPHYLINID^E. 



This numerous tribe, of which the common British insect, the Ocyptu olens, or Devil's Coach- 

 horse, is a typical example, is distinguished by the much abbreviated elytra, these organs, in all but 

 a few genera, being so reduced in length that they leave nearly the whole of the upper surface of the 

 abdomen exposed. They are, however, always of oblong or square form, with straight hind margins, 

 and meet in a straight suture. The membranous wings, of normal length, and adapted for active 

 flight, are closely folded beneath. In correspondence with the abbreviation of the wing-covers, the 

 upper sides of the abdominal segments are of horny texture, like the under ; the segments, further, are 

 all mobile, and the abdomen is thus capable of flexure in all directions. The habit of curving the tail 

 upwards is very charac- 

 teristic of these insects, 

 the tip of the body being 

 used for pushing back 

 the membranous wings, 

 after flight, under the 

 elytra; and in some small 

 species it is carried 

 habitually in a curled-up 

 position, even in run- 

 ning. Many Brachelytra 

 are of active predaceous 

 habits, like Carabidse ; 

 and in some of the genera, 

 in which the elytra are 

 much longer than in the 

 majority, the resem- 

 blance to Carabida? of 

 the TruncatipennaB group 

 is very great : but in 

 these, as in the rest of 

 the tribe, the totally 

 different form of the 

 chief parts of the mouth 

 shows that we have to 

 deal with a different 

 type. The maxillse differ 

 from the same organs in 

 the Adephaga in the 

 outer lobe being never 

 palpiform, though some- 

 times two-jointed, and the labium in being fully exserted beyond the upper edge of the mentum, 

 the latter of which plays a subordinate part the reverse, in fact, of what we see in the Adephagous 

 tribe. This tendency towards a full development of the elements of the labium may be noted as an 

 approximation to the mouth structure of the order Orthoptera, and as indicating a low position in 

 the scale of specialisation of the Coleopterous tribes. 



Many of the genera depart from the rule among the Pentamera section with regard to the number 

 of tarsal joints. In some the four anterior feet have only four joints each ; in many others four joints is 

 the number to all the feet ; and, again, some aberrant genera have only three joints. These exceptional 

 cases, however, do not show any resemblance in the rest of their structure to the sections Tetramera 

 and Trimera, to which they would be referred if the number of the tarsal joints were the sole character 

 relied on. The antennae are variable in form and in number of joints (nine to eleven) ; in extreme 

 cases they are club-shaped. The sternal structure in the majority is remarkable for the atrophy or 

 disappearance of the breastplates of the first segment, and partly of the second. In the insects thus 



ocvprs OLEXS (DEVIL'S COACH-HORSE) AND LAKVA. 



