ABERRANT WOOD -BEETLES. 



101 



Tribe X. 



ABERRANT WOOD-BEETLES. 



Lignivora aherrantia. 



Uuder the title of aberrant or exceptional Wood- beetles, as stated in 

 the general remarks upon the Serricornes, we have included, for the 

 sake of brevity and convenience, a number of small families, some of 

 which have but a remote relationship to the others, but which cannot 

 naturally be united with any of the larger tribes. 



This tribe contains two very dissimilar groups. In the first, which is 

 composed of the family of Ptinida^, including the sub-family of Bostri- 

 chides, the body is rather short and thick, or moderately elongated and 

 cylindrical, and the head is bent down and mostly or wholly concealed 

 under the vaulted or hood-like thorax. 



In the other group, which includes the small families of Lymexylo- 

 nidai, Cupesidiie and LyctidiE, the body is much elongated and often 

 depressed, and the head is free and exposed, and sometimes attached 

 to the thorax by a short neck. These three families combined do not 

 contain more than a dozen known American species, most of which are 

 rare, and are found mostly under the bark of decaying trees. Many 

 authors include them in some one or other of the larger families. 



Family XXXVI. PTINID.E. 



This is a family of moderate extent, composed of small insects, rarely 

 exceeding a quarter of an inch in length, and often only about half that 

 length, and usually of a cinnamon-brown color, sometimes black and some- 

 times ornamented with patches 

 of whitish scales. Their most 

 distinctive character is the vault- 

 ed or hood-like form of the ante- 

 rior part of the thorax, the head 

 being bent under it or partly re- 

 tracted within it, so that it can 

 be scarcely or not at all seen 

 when the insect is viewed from 

 above. The antenna3 are gener- 

 ally filiform, but in Bostrichus 

 they terminate in three larger 

 joints. The tarsi are simple. The larvte resemble those of the Lamelli- 

 corn beetles, in miniature, being soft and white, and usually lying in a 

 curved or semi-circular position. They have six legs, but do not use 

 them in crawling in the usual way, but draw themselves along upon 

 their sides. 



a, Anobium paniceum, Fab. : b. ita antennio 

 Nus BUUNNEUS, Dufs. — after Kiley. 



