METAZOA INSECTA. 467 



Pack.), possesses in the young larval state a pair of antler- 

 like horns (PI. 1187, fig. i, side view; fig. 2, front view 

 of head and prothoracic horns, greatly magnified), the 

 use of which is unknown. When older the larva loses 

 these organs, as seen in fig. 3. 



Among the more specialized of the Bombycine moths 

 is Centra cinerea Walk., in which the anal prop-legs have 

 become two long tubes (PL 1188, fig. i), each containing 

 a highly colored tentacle or whip with which Cerura 

 lashes its body to drive away its enemies. 1 The dull-col- 

 ored moth is seen in fig. 2. 



The American silk moth, Teka polyphemus Linn., of 

 the family Saturniidae, is a good type form of the group 

 of moths. The thoracic and abdominal regions of the 

 larva (No. 1189, larva, pupa, cocoon, and imago) are 

 large, while the head is small. The mouth parts are effi- 

 cient biting organs. The thoracic legs are weak but the 

 four pairs of prop-legs are strong. The caterpillar spins 

 a cocoon within which the pupa remains motionless for 

 a longer or shorter time, according to temperature. Dur- 

 ing this time its appendages are encased in sheaths and 

 are fastened closely to the body. When ready to trans- 

 form, the pupa secretes a liquid which dissolves the gluey 

 substance holding the silken threads together, so that 

 the pupa emerges without doing great damage.' 2 



The moth (No. 1189) has a robust body, the thorax 

 being the largest part. The three regions are not closely 

 connected, and the junction of the thorax with the abdo- 

 men is broad. 



The antennae are either thread-like or feather-like, and 

 as a rule these organs in the male are much broader than 

 in the female. The mouth parts are vestiges and the 



1 Scudder. Trans. Amer. Ent. Soc. Phila., 1877, p. 77. 



2 Trouvelot states the adult escapes without breaking a fiber. 

 Comstock says, "and breaking the threads," the adult escapes 

 through the large round hole. 



