Mr. G. Lewis on Eretmotus and Epiechinus. 231 



XXVII. — On Eretmotus and Epiechinus (Histeridse). 

 By G. Lewis, F.L.S. 



[Plate XIX.] 



Last spring I made another excursion in Algeria, and, 

 searching diligently as occasion ofFeied for Myrmecophilous 

 HisteridiB, I succeeded fairly well as regards Eretmotus ; but 

 I was not so fortunate in respect to Sternoccelis as during a 

 somewhat similar ramble in 1888. I found three new species 

 of Eretmotus and one new Sternoccelis ; and my additional 

 material makes it clear that an Eretmotus I took in 1888 and 

 erroneously referred to E. apjfroccimans, Fairm., is an 

 undescribed species. 



The best specific characters in Eretmotus lie in the structure 

 of the prosternuni, and figures of tliis part of seven species are 

 given here. In the figures the anterior lobe of the proster- 

 num is not shown, the suture before the keel being the limit 

 of the drawing. The Plate also gives some outlines of the 

 sterna of three species of Epiechinus, a genus lately formed to 

 receive Onthophilus costipennis, Fahr., and allies. The genus 

 at present contains, besides five African species, four from 

 Asia, viz. E. arhoreus, Lew., taprohance, Lew., birmanus. 

 Lew., and OntJiophilus hispidus, Mars. ; and the structure of 

 the sternal plates is very curious. 0. hispidus, Mars., is 

 described in the ' Abeille,' i. 1864, p. 340, from specimens 

 taken in Celebes by Wallace, a species supposed by Marseul 

 to be Paykull's Hister Mspidus from the " East Indies : " but 

 this is more than doubtful. Figure 9 is drawn from an 

 example taken lately at Port Darwin by Mr. J. J. Walker, 

 and is, I think, Marseul's species, the type of which I 

 examined in Paris last May. 



On a general study of the Histeridje, made with such 

 knowledge as I have derived from the habits of about one 

 hundred and fifty species I have seen alive in various parts of 

 the globe, it appears that the elytral stride serve for what may 

 be termed guiding-lines — that is, that a species whose habits 

 do not necessarily constrain it to move in a direct or straight 

 line is guided in its movements or receives assistance in 

 going straight from the dorsal strige. The genera Hister and 

 Platysomuy especially the cylindrical species, contain types of 

 this kind, and Teretrius aud Tryponceus consist of species 

 without stride, and with them no guiding-lines are necessary, 

 as the species all frequent holes drilled in timber by wood- 

 boring beetles, where they cannot move to the right or to the 

 left. Eretmotus is another instance, but of a different kind, 



