422 The Great Water-Beetle. 



equivalent for food ; the heat- supplying materials are econo- 

 mized, and; like a lamp slowly burning, life goes on during the 

 period of hybernation. 



The other, tenanting the sheltered valleys, where the snow 

 never remains long and food is readily obtained, simply digs 

 or burrows under a stone, and feeling no necessity, cares not 

 to build himself a house. 



In the same range of mountains lives that rare and singular 

 little animal the Aplodontia lejporina, of which I shall have 

 something to say in my next. 



THE GREAT WATER-BEETLE {DYTICUS 

 MABGINALIS.) 



BY REV. W. HOUGHTON, M.A., P.L.S. 

 {With a Tinted Plate.) 



Evert searcher of ponds and ditches for animals wherewith 

 to stock his aquarium is, doubtless, familiar with the large 

 water-beetle {Dyticus marginalis) , of active habits and pre- 

 daceous disposition. In the present paper I purpose to say a 

 few words about this king amongst Aquatic Coleoptera, I will 

 first of all draw attention to his habits and form, and then offer 

 a few remarks on the examination of some parts of his 

 internal organization, with especial reference to the digestive 

 apparatus. The great water -beetle is a capital subject for insect 

 dissection. Its large size renders the task of an anatomical in- 

 vestigation, comparatively speaking, simple and easy. It is, 

 moreover, widely distributed throughout this country, and 

 readily procurable at most seasons of the year : in the winter, 

 however, it buries itself in the mud, and is difficult to meet 

 with. I have searched in vain a couple of hours a-day for 

 specimens of Dyticus, during the winter, in ditches where the 

 summer previously I could obtain any number. 



The great water-beetle is, both in its larval and imago 

 state, one of the most voracious insects in existence. If kept 

 in an aquarium, his predaceous disposition soon manifests itself. 

 Woe betide the unfortunate stickleback or newt that is once 

 caught and held by the strong mandibles of this fresh-water 

 tyrant. It little matters what is the size of the victim 

 attacked. I have seen Dyticus rush upon a full-grown smooth 

 newt, and no twistings and writhings of his eftship was of 

 any avail. Burmeister has recorded of a kindred genus 

 (Gybister Roselii), that it devoured in the short space of forty 

 hours two frogs, and that so rapid was the digestive process, 



