68 THE CLASS OF INSECTS. 



thoracic ring enlarged, swelling and rounding 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 

 mesothorax. The thoracic 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 metathorax, 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. 

 The prothorax of the larva disappears, and that of the pupa 

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

 skin is thrown oflT, 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 by 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 Ephemera., soon after it has taken its flight. Westwood also 

 considers this subimago skin identical with that covering the 

 bodies of coarctate Diptera, as in EristaUs. 



Newport states, that when the imago of Sjihinx is about to 

 cast 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 within the 

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

 drawn out of the rent. In the Butterfly the wings mature in a 

 few moments, but those of Sj^hinx being thicker, require two 

 or three hours. 



Newport (Philosophical Transactions, London, 1832 and 

 1834) has detailed with great minuteness the internal changes 

 of Sphinx ligustri while transforming. The most marked 

 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 Meloe. The 

 development of the latter insect will be noticed bej'ond. 



Sir John Lubbock has described the singular metamorphosis 

 of Lonchoptera^ which he considers to be allied to Sargus, 

 though the adult stages difler greatly. The larvae are oblong 



