90 HYMENOPTERA. 



from the trunks of barked oaks, which had dried, and were 

 scorching in a July sun. The materials used by insects in 

 building are, we believe, generally influenced by circum- 

 stances ; as an illustration of which, I may quote the fact, 

 recorded in my observations on the habits of humble-bees ; 

 Bombus muscorum, that usually constructs her nest of moss, 

 on one occasion constructed it entirely of short horse-hair, 

 which was accumulated in a stable window, close at hand, 

 from the currying of horses. 



I may be permitted to mention the publication, during the 

 past season, of my second Monograph on the British Acu- 

 leata, it contains descriptions of all the known species of 

 Formicida, Fossores and Vesjridce. It is now twenty-three 

 years since Shuckard's excellent Essay on the Fossores ap- 

 peared, and during that period, nine new species have been 

 discovered, three in the Essay proved to be of foreign origin, 

 and the opposite sex has been discovered of twelve species 

 of which previously only one sex was known. An ample 

 amount of facts and observations on the insects described is 

 added, and every endeavour has been made to render the 

 volume as complete as possible ; the portion treating on the 

 Formicidce has been rendered far more correct than it other- 

 wise could have been, by an interchange of specimens of the 

 species with the authors of recent Monographs on that family, 

 Dr. Nylander, Dr. Myer, Foerster and Dr. Roger ; the Fos- 

 sorial group have had the advantage, in many cases of diffi- 

 culty, of the opinion of M. Wesmael, who has had oppor- 

 tunities of consulting the typical specimens described by Van 

 d. Linden. 



The subject of arrested development in the larva of Hy- 

 menoptera has frequently attracted attention, but the cause 

 remains, as far as I am aware, an impenetrable mystery; 



