178 MR. NEWPORT ON THE NATURAL HISTORY, ANATOMY, 



the inferior and posterior parts of the hody of the pseudo-larva, thrust backwards in a 

 packet, as it is slipped off at the period of change. In the absence of discovery of the larva 

 itself, before it is full grown, this cast skin enables us to indicate its general form and 

 economy, at that period of its existence, as surely as the fossil bone enables the compa- 

 rative anatomist of the Vertebrata to indicate those of the habitant of a former world. 

 The skin of the larva is fissured at the period of change along the median line of the pro- 

 thoracic segment, and is extended forwards to the head and backwards to the meso- and 

 raeta-thoracic segments, exactly as in other insects. By carefully removing this skin from 

 the pseudo-larva, and relaxing it in water for some hours, and then inflating it gently with 

 a blowpipe, the general form of the larva is made apparent. It is a fat, yellow-coloured, 

 elongated grub, with six short legs, formed of short coxal, femoral and tibial joints, covered 

 with delicate scattered hairs, and with tarsi, each of which is a single joint, armed with a 

 single short strong horny claw. The tarsal spines which exist in the very young Meloe on 

 each side of this claw, — and which are of so much importance to the insect at that period 

 of its existence in enabling it to cling firmly to its victim, and, relatively with other parts, 

 are so large and conspicuous, that Leon Dufour derived from them the character of his 

 genus Trvimgulmus, — have entirely disappeared at previous changes of the tegument. In 

 like manner also the caudal styles have been removed, being reduced to mere pointed 

 tubercles, as in the larva of Cryptophagus* , preparatory to their complete obliteration in 

 the pseudo-larva. The body is arched, slightly convex, and formed of fourteen segments, 

 with a few scattered elongated hairs, as in the very young state ; and also, as I have 

 already mentioned, is covered on every part with multitudes of microscopic ones, scarcely 

 one-thousandth of an inch in length, each proceeding directly from the centre of nearly 

 every cell in this cast envelope. The segments of the body are nearly all of the same 

 dimensions, and thus give to the larva a more uniform and less articulated appearance 

 than that which it presents in its earliest state, when the segments of the thorax greatly 

 preponderate. 



The external organs of respiration have undergone but little change, either in form or 

 in situation ; excepting only that the second pair of spiracles are now of the same size as 

 those of other segments. The small size of the whole, relatively to that of the body, seems 

 to indicate a minimum degree of activity in the function of respiration, and consequently 

 a sluggish mode of life, similar to that of the Bee-larva, in the abode of which the Meloe 

 is a parasite. The spiracles at this period are not larger than those of the Bee-larva, ex- 

 cepting the anterior pair. The whole are nearly circular in form, and their entrance is 

 protected by a raised horny margin. Internally they are lined by a membrane made up 

 of extremely minute but distinct cells, which form a layer that is continuous with the 

 mucous lining of the trachea. This lining is removed in connexion with the cast skin 

 from the whole of the ramifications of tracheae connected with each spiracle ; and its deli- 

 cate, hair-like, tubular, uniform divisions, which pass off from the main stems at acute 

 angles, further prove that the capacity of the tracheae, and consequently their function as 

 respiratory organs, is insignificant and restricted. 



This cast envelope of the full-grown larva shows that, up to this time, the head has 



* Linn. Trans, vol. xx. p. 352. tab. 14. fig. 34. 



