410 STAPHYLiNiDiE. [^Homalium. 



and only one from Tropical South America ; a considerable number also 

 have recently been described from Australia and New Zealand ; they 

 are distinguished by their usually long parallel-sided form, long elytra, 

 and more or less spinose tibiae ; all the tarsi are five-jointed, the first four 

 joints being short, of about equal length, and taken all together either 

 shorter or only slightly longer than the last joint. 



There are about fifty European species, of which about thirty are 

 British ; some of these are very distinct, but many of them are closely 

 allied and require great care in distinguishing them, as the differences 

 are merely comparative ; the best plan appears to be to separate them first 

 into sections according to the various sub-genera into which they have 

 been divided, and then to tabulate them under these sections. 



, The sexual differences are, with one or two exceptions, very slight, and 

 do not require separate notice ; the male has the sixth ventral segment 

 of hind body truncate or slightly emarginate at apex, and the seventh 

 somewhat more projecting than in the female. 



The larva of Homalium vile is described and figured by Ferris, Ann. Fr. 1853, 

 p. 576, pi. 17, fig. 49-55 : it is about 3 mm. in length and is shaped almost exactly like 

 that oi Phloeupora reptans, but diflers in being of a uniform livid reddish colour, in 

 its longer head, and the different formation of the apical abdominal segments and 

 appendages ; the eighth segment is not prolonged above the ninth, and the ninth is 

 narrow and bears a short anal appendage, and two rather long cerci, of which the 

 first joint is as long as the anal appendage, and is longer than the second joint ; the 

 insect has the power of widening or lessening the distance between these cerci at will ; 

 above each antenna there is a small reddish ocellus. 



The larva of H. pnsiUum is smaller than the preceding, and differs in having five 

 ocelli on each side of the head, and in its longer anal appendage which is about as long 

 as the cerci ; these latter have the first joint double as long as the second. 



Both these larvaj, like those of Phloiopora and Placusa, live in the galleries of 

 Tomicus and devour the pupaj of species of that genus. 



I, Form elongate, parallel ; elytra not dilated behind, hind body elongate, more or 

 less parallel-sided for the greater part of its length. 

 i. Antennas pilose ; forehead almost always furnished with a line or fovea before 

 ocelli.* 

 1. Hind body deeply impressed within lateral margin. 

 A. Upper surface glabrous ; elytra confusedly punctured. 



a. Last joint of maxillary palpi double as long as the preceding ; tibia) 



spinose ; form less flat ; thorax with impressions rather strongly marked. 



Section 1. (Homalium, i. sp., p. 411.) 



b. Last joint of maxillary palpi not much longer than penultimate ; tibiae 



feebly spinose ; form flat, dull, very small ; thorax with impressions 

 strongly marked. 



Section II. (Phloeonomus, Heer, p. 416.) 



C. Last joint of maxillary palpi about three times as long as the preceding j 

 tibiffi spinose ; form rather flat ; thorax with impressions shallow. 



Section III. (Xylodromus, Heer, p. 417.) 



* The only exceptions are H. vile, H. brevicorne, H. gracilicornc, and H. iopierum 

 (iu the sub-genus Pliyllodrepa). 



