68 THE CLASS OF INSECTS. 



tiioracic ring enlarged, swelling and ronnding above and on the 

 .sides, and with this increase in size drawing the nieta-thorax 

 forwards. The first visible portion of the pupa beneath is the 

 inesothorax. The tlioracie legs of the larva are now con- 

 stricted at their base, and have become useless. 



In the next stage, the most important change noticed is in 

 the metatliornx, which now becomes broadly heart-shaped. In 

 a succeeding stage, the whole thorax bulges out, and is much 

 larger and clearl}- distinguished from the head and abdomen. 

 Tlie prothorax of the larva disappears, and that of the jjupa 

 takes its place. The occiput of the pupa, just before the larva- 

 skin is thrown off, can be distinctly seen under the larval occi- 

 put, pushing aside each half of the latter. 



In the last stage of Bombus just before the imago leaves its 

 cell, the body and limbs are surrounded b}^ a thin pellicle. 

 This pellicle also envelops the moth, just before it leaves the 

 pupal state, and is cast off when it moults the pupa-skin. This 

 is probably identical with the skin cast by the active subimago 

 of E'phemera^ soon after it has taken its flight. Westwood also 

 considers this subimago skin identical with iliat covering the 

 bodies of coarctate Diptera, as in Eristalis. 



Newport states, that when the imago of Sj^Mnx is about to 

 east off the pupa-skin the abdominal segments are elongated 

 beyond their original extent, this being the first part of the 

 insect that is entirely freed from its attachment witliin the 

 pupa-case. After this the thorax slits down, and the body is 

 drawn out of the rent. In the Butterfl}" the Avings mature in a 

 few moments, but those of S/)hinx being tliicker, require two 

 or three hours. 



Newport (Philosophical Transactions, London, 1832 and 

 1834) has detailed with great minuteness the internal changes 

 of Sjyhinx llgvstri while transforming. The most nua-ked 

 changes are in the nervous and digestive systems. 



Several anomalous modes of metamorphosis have been ob- 

 served, one in Diptera and the other in Sitaris and JMoe. The 

 development of the latter insect will be noticed beyond. 



Sir John Lubbock has described the singular metamorphosis 

 of Lonchojotera, which he considers to be allied to /Sargus, 

 though tlie adult stages differ greatly. The larva; are oblong 



