178 Prof. J.C. Schiddte on the Classification 
spiracles. With the exception of the middle line, this large 
head will be found filled by the powerful flexors of the mandi- 
bles, reaching to the foramen occipitale, which is very large and 
entirely transferred to the under surface of the head. The head, 
then, is for the greater part hidden in the prothorax as in a 
sheath, fixed all around and directed by the powerful muscles 
of the neck. The whole of the part which is placed inside the 
prothorax is only sparingly chitinized; but the action of the 
muscles of the neck extending between the outside of the skull 
and the walls of the prothorax makes up for any loss of support 
which could arise to the mandibular muscles from the want of 
hardness in the skull. During the act of burrowing, the pro- 
thorax is firmly ensconced between the walls of the gallery, the 
numerous grains of chitine with which its surface above and 
below is generally beset increasing the firmness of its posi- 
tion; and thus every requisite condition is provided—a firmly 
placed prothorax affording support for the muscles of the neck 
in guiding the head forwards and backwards and to the sides, 
and the skull inserted as in a sheath giving support to the 
enormous mandibular muscles. 
The immense size of the head and its deep insertion into the 
prothorax, of course, are the causes of the peculiar shape and 
unusual size of the latter part, which has further contributed to 
confound the views of entomologists on the structure of the 
larvee of Buprestidee*. It has been overlooked by all that in 
this case one part of the prothorax is developed at the cost of 
the others—namely its anterior portion, the so-called collar (col- 
lare prothoracis), which is found in all larve and all imagos of 
insects with more or less inserted neck, but which in the larvee 
now before us is immensely increased in size. In my paper 
on the larve of Coleoptera, published in the ‘ Naturhistorisk 
Tidsskrift,’ I describe the dorsal part of this collar as preetergum 
pronoti. The rest of the prothorax, which is elsewhere much 
the larger, and which serves the locomotory system by accom- 
modating the fore legs, is in this case to such a degree reduced 
that it seems to be entirely wanting, and the large spiracula 
thoracica have not been able to find room as usual on the pro- 
thorax, but have been transferred to the lateral folds of the next 
ring, pleuree mesothoracis. The larve of Trachys being de- 
scribed as possessing a free head and short legs, it will, no 
doubt, be found that the larve of Buprestidee will show the same 
* In the Mém. de l’Acad. des Se. de Lyon, 1851, pp. 116-120, M. Perris 
has given a minute summary of the discussion between Goureau, Lucas, 
and Léon Dufour on this subject. Although each of the four authors now 
and then has got hold of the clue for a moment, they have always lost it 
again, and none of them has succeeded in solving the problem. 
