38 



The prothoracic ring is unchanged, while the metathoracic ring is already 

 much diminished in size, and the outlines of the primitive form of the meso- 

 scutum arc indicated. 



Fig. 2 represents an extremely interesting stage; the prothoracic ring 

 is now much smaller; the mesothorax is large; the scutum is well marked; 

 while the metathorax indicates the scutum deeply hollowed out. apparently 

 to receive I he mesoscutellum. 



Figs. .'), 3a, 4, 4a, 5, ha, represent ;i more advanced stage. The thorax 

 is more swollen, and has assumed somewhat of the characteristic form of I he 

 imago, lni) the abdomen is still as seen in the larva. 



In figs. 6, 6a, the semi-pupal condition is nearly completed. The pro- 

 portions of the three thoracic segments now approach those of the imago. 

 The prothorax is still undifferentiated ; but the scutum is well marked, though 

 the drawings do not indicate that the scutellum has been separated from the 

 scutum. The abdomen is now much contracted, and of the pupal proportions. 



Fig. 7 is a dorsal view of the end of the semi-pupal stage. 



Fig. 8 represents the pupa. Owing to the paralyzed, enfeebled state of 

 the larva, the ends of the wings have not reached the end of the depression 

 in the under side of the abdomen. 



The facts here given are, however, sufficient to show that the transfor- 

 mation of the larva into the pupa is a very gradual process, and may be com- 

 pared with the stages that I have already showed to exist in the semi-pupal 

 condition of Bombus* It seems that the pieces of the thorax are indicated 

 during this stage, but that the scutum of the prothorax and metathorax do not 

 separate until the close of the pupal life, while the mesoscutellum does not 

 become differentiated until after pupation. This process must go on in the 

 hypodermis of the pupa, which is destined to form the imaginal integument. 



§ 11. — Secondary sexual characters of the imago. 



The more apparent sexual characters of the adult Phalsenids consist in 

 the antenna' being ciliated or pectinated in the male, and simple or suit- 

 simple in the female. The head in front is wider in the female than in the 

 male, as in other Lepidoptera. The wings, particularly the anterior pair, are 

 broader and blunter at the apex in the males than in the females. The abdo- 



• Observations on the Development and Position of the Hymenoptera. — PnhtciUiii's liost. Sue. Nat. 

 Hist., x, 1866,379. 



