38 Mr. John Curtis's Descriptions 



This curious insect not liaving been yet discovered in Britain, 

 I have added a figure of the beetle (fig. 33 rt, the natural size); 

 and as there are many peculiarities in its structure, and it departs 

 considerably from the type of the Cucujidce, I have determined to 

 add dissections of the mouth, which will be serviceable also in 

 exhibiting the differences between the same insect in the larvae 

 and imago states. In fig. 34, which shows the underside of the 

 head of the beetle, the two long processes, like bulls' horns, are 

 very remarkable (fig. 34 «), and their use inconceivable, unless 

 they are employed to divide the laminae in the decayed trees, 

 between which the Prostomis delights to nestle, in invisible spaces, 

 which from its depressed form it is enabled to do, and the larvae 

 are still thinner, being apparently composed of nothing but their 

 transparent horny covering, with an alimentary canal shining 

 through. The labrum (fig. 35) is semi-orbicular, and attached to 

 an elongated or lobe-shaped clypeus. The mandibles, which pro- 

 ject, are unequal, one being very much dilated on the outside 

 (fig. 36), and they have both a series of teeth on the inside, with 

 larger ones at the apex. The maxillae comprise two remarkably 

 long lobes, the outer one articulated, at the base of which arises a 

 still longer palpus of four joints (fig. 38). The labrum is singu- 

 larly shaped, forming a flattened pointed tongue : the palpi are not 

 attached to the base, and they are long and triarticulate (fig. 39). 

 Tn the genus Cucujus, at least in the minute species I dissected in 

 the British Entomology,* the jaws, although porrected, are not 

 particularly developed, and they are notched internally, more like 

 the Hctcromcra : the oral organs are not elongated, and all the 

 palpi have fewer joints, viz. 3 and 2. It is evident that the great 

 development in Prostomis is necessary to obviate the obstruction 

 occasioned by the cephalic horns, and it is very singular that in 

 the larva there is no indication of those processes. The beetle is 

 furnished with ample wings, and the legs, like those of Cucujus, 

 are very short ; the hinder pair very remote, and it is perfectly 

 tetramerous (fig. 40), whilst Cucujus f err ugineus or C. testaceus are 

 pentamerous. 



As Prostomis inhabits oaks and chesnuts, and is widely distri- 

 buted in France and Germany, I hope it may some day find its 

 way legitimately into our English fauna. The beetles with this 

 larvae were abundant near Pau in March, in the trunks of decay- 

 ing and very aged chesnut trees. They preferred portions seve- 

 ral feet from the ground, and were secreted between the lamina of 

 the wood, where it was quite wet, rotten and soapy, resembling 



* Curt. Biit. Ent. pi, and fol. 5i0. 



