Sept., 191 1.] Wheeler: Notes on Beetles of Genus Xenodusa. 163 



NOTES ON THE MYRMECOPHILOUS BEETLES OF 



THE GENUS XENODUSA, WITH A DESCRIPTION 



OF THE LARVA OF X. CAVA LECONTE.' 



By William Morton Wheeler, 

 Boston, Mass. 



Our knowledge of the singular beetles of the North American 

 genus Xenodusa. in contrast with that of the European species of 

 the closely allied genera LoJiiccJuisa and Atcinclcs, increases very 

 slowly. This is unquestionably due to the much greater scarcity and 

 more local distribution of the species of Xenodusa. In a paper pub- 

 lished in 1907' I reviewed the scattered observations of other authors 

 on these beetles and added a few of my own. After four years I am 

 able to make a further slight contribution in the form of a descrip- 

 tion of the larva of X. caz'a, together with a few notes on the hosts 

 of this and of some of the western species. 



Wasmann has shown that Loniechusa struniosa is homoecious, or 

 has only one host, the typical form of Formica sanguinca, with which 

 it lives throughout the year, whereas the species of Atemelcs and 

 Xenodusa are heteroecious, since they breed during the summer in 

 the nests of Formica but hibernate with ants of a different genus. 

 The winter host in the case of Atemelcs is Myrmica rubra or some 

 one of the closely allied species (scabrinodis, lez'inodis, rugulosa, etc.) 

 which were formerly regarded as mere subspecies. Xenodusa, how- 

 ever, winters in the nests of Camponotus species. The definitive and 

 almost certainly the primitive host is, therefore, in both genera, 

 Formica, while the winter host is a later or secondary acquisition. 

 The genus Lomechusa probably represents a very primitive condition 

 so far as its relation to a single host is concerned, though in other 

 respects it certainly represents a more advanced stage of parasitism 

 or of dependence on its host. 



' Contributions from the Entomological Laboratory of the Bussey Institu- 

 tion of Harvard University, No. 41. 



-The Polymorphism of Ants, with an Account of Some Singular Abnor- 

 malities Due to Parasitism. Bull. Amer. Mus. Nat. Hist., XXiHI, 1907, pp. 

 1-93, pis. I-IV. 



