86 —- Prof. J. C. Schiddte on the Tunnelling Coleopterous 
adapted for a similar life, the 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 
larvee of Heterocerus and Elmis. All these Coleoptera are dis- 
tinguished by the peculiar structure of the mandibles, which, 
both in imagos and in larve, are constructed as pincer-shaped 
grinding-instruments carrying several teeth on their terminal 
part. The larve 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 Si/pha 
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 Staphylini, Scaritint amongst Carabide, Ce- 
briones amongst Elateride. 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 antenne, is distributed into several genera, 
the characters of which will be explained further on. 4H. von 
Kiesenwetter has supplied excellent materials for the difficult 
distinction of the species, to which we offer 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 asa 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 dark 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 mesosternum. 
