36 Prof. J. C. Scliiodte on the Tunnelling Coleoptei'ous 



adapted for a similar life, tlie beetle wandering about on the 

 shore^ protected entirely from the sun and hidden from its ene- 

 mies by means of a portable roof of clay. Heterocerus obtains 

 the same protection by tunnelling the shore, whilst Parnus and 

 Elmis represent still more decided modifications for living in 

 water, the former crawling about the water-plants under the 

 surface, whilst the latter clings to the under surface of the 

 stones on the bottom. It is one of the most striking examples 

 of typical unity coupled with extreme biological adaptation for 

 different modes of life, that in all these animals the structure of 

 the mouth remains almost entirely the same, even in the smallest 

 details, not only in Heterocerus and Parnus, but even in the 

 larvse of Heteroce?'us and Elmis. All these Coleoptera are dis- 

 tinguished by the peculiar structure of the mandibles, which, 

 both in imagos and in larvae, are constructed as pincer-shaped 

 grinding-instrumcnts carrying several teeth on their terminal 

 part. The larvfe possess two maxillary lobes. Hitherto much 

 stress has been laid on their external shape, which is very vary- 

 ing ; but this view will have to be abandoned here as everywhere. 

 Even the larva of Cytilus is entirely different from that of Byr- 

 rhus in appearance, being much more like the larva of Silpha, 

 though the imagos are so very much alike. 



Heterocerus and allied genera occupy exactly the same position 

 with regard to the other Coleoptera we have mentioned as Bledii 

 occupy amongst Staphyliui, Scaritini amongst Carabidse, Ce- 

 hriones amongst Elaterida^. They exhibit the fossorial modifica- 

 tion of the type, are the moles of the family, and form a special 

 group (Heterocerini), which, according to the structure of the 

 mouth and of the antennse, is distributed into several genera, 

 the characters of which will be explained further on. H. von 

 Kiesenwetter has supplied excellent materials for the difficult 

 distinction of the species, to which we oflfer some further addi- 

 tions. The principal characters of the group are as follows : — 



When the head is pushed forwards, the closed mandibles work 

 both as a wedge and as a shovel. These latter are proportionally 

 long, their upper surface somewhat hollow, the outer margin 

 bent upwards, and with a tooth on the very edge; the terminal 

 part is protruding, carries four teeth, and is (in the males of 

 some species, particularly in large and powerful specimens) pro- 

 longed and curved upwards ; the inner lobe is greatly developed, 

 with a free apex and the inner margin furnished with spines 

 forming a comb ; the molar tooth is very large and grooved ; the 



the (lark colour of the other integuments. When the head is bent in, the 

 prosternum is covered up by the organs of the mouth, the trochanters of 

 the first pair, and the mesostei'num. 



