182 MR. NEWPORT ON THE NATURAL HISTORY, ANATOMY, 



and has ceased to feed, as at the period at which I have found the full-grown Meloe, the 

 muscles effect a complete alteration in the segments hoth relatively and individually. The 

 abdominal segments, which are the largest while the larva is feeding, are quickly reduced 

 in size when fresh nourishment has ceased to be supplied ; while those of the thorax are 

 enlarged, and duplicatures of tegument are formed between each by the shortening of the 

 longitudinal and diagonal muscles. 



In the pseudo-larva of Meloe (fig. 13) these changes have only commenced ; but when the 

 insect passes to the nymph or pupa state (fig. 15), the alteration is carried to a very great 

 extent. The longitudinal muscles of the abdominal segments occasion, by their powerful 

 contraction, broad reduplications of the tegument, the posterior margin of one segment is 

 made to cover the anterior of the one next behind it, and the whole are much shortened. 

 The force of development in this region is from behind forwards, the effect of which is to 

 occasion a rapid enlargement of the head and of the thoracic segments, and the coalescence 

 of some of the latter by aggregation and anchylosis. This is carried to the greatest extent 

 in the segments of the middle of the body, which form the union of the thorax and abdomen 

 in the imago. In some insects the fifth segment of the larva is reduced to its minimum, 

 and disappears as a sectional portion of the animal, its rudiments only being left. In the 

 nymph or pupa of Meloe the metathoracic or fourth segment is the shortest, the fifth being 

 further shortened at the next change. 



The immediate result of the altered proportions of the abdominal segments, and their 

 removal forwards by the action of the muscles on the tegument, is a re-induction of the 

 forces of growth in the appendages of the thoracic and cephalic segments, and a conse- 

 quent enlargement of the segments themselves, more especially those of the head. This 

 region in Meloe' is enormously enlarged, as compared with the head of the larva. But 

 this does not result, as M. Ratzeburg seems to think, from certain observations he has 

 made on Hymenoptera, from a coalescence of the head of the larva with the segment next 

 behind it, but it is entirely due to the rapid growth and expansion of all parts of the head 

 at the period of transformation. 



The change effected while the larva is passing to the pseudo-larva state, is a com- 

 mencement of a re-induction of the growth of the appendages of the head and thorax. 

 The legs, then reduced to tubercles, are soon redeveloped beneath the tegument of the 

 pseudo-larva in an entirely new form, with jointed tarsi, ready to be elongated at the 

 instant of change to the nymph. 



In addition to the redevelopment of these parts, the rudiments of new organs are pro- 

 duced. The internal respiratory structures are extensively affected by the changes, as is 

 the case in all insects on becoming pupae, and the result is to occasion the expansion of a 

 fold of the tegument, at the sides of the metathorax (fig. 16 a), in which some ramifications 

 of trachese are included. The growth of this fold in Meloe is soon arrested, and it becomes 

 the future rudimentary elytron of the imago, as in other insects it is the anterior wing. 



Minor causes, which it is unnecessary to mention here, not only occasion these parts to 

 be developed to a greater extent in some species than in others, but also effect the produc- 

 tion of a second fold from the metathorax, the posterior wing. 



Besides these there are other important changes in the tegument in these transforma- 



