1910.] NATURAL SCIENCES OF PHILADELPHIA. 299 



III. Observations. 



To the family of Saturnids belong those moths which are silk 

 weavers par excellence in the caterpillar state. Among our most common 

 native species are Callosamia promethea and Samia cecropia, which 

 emerge from the pupa case in May or June. Much has been written of 

 the keenness of the mating instinct in promethea and my own observa- 

 tions confirm these accounts. The moths mate and lay eggs which 

 hatch in from eleven to fourteen days and the caterpillar pupates in 

 from five and a half to eight weeks, depending upon its supply of food. 

 The pupae of C. promethea are very like those of P. cynthia and the two 

 may be easily confused. This is especially true since the caterpillar of 

 P. cynthia will live upon the same food plants as that of C. promethea, 

 but in this case it is smaller than usual and weaves a cocoon just like 

 that of C. promethea. The number of chromosomes in an equatorial 

 plate differs in the two and it was sometimes necessary to use this means 

 of identifying these two species. 



The testes inLepidoptera originate as paired glands. They are situ- 

 ated under and on each side of the intestine in the region of the sixth 

 segment. In moths of the family Saturnidee these organs are paired 

 and develop in size until just before the moth emerges, when the ripe 

 spermatozoa are discharged into the greatly enlarged vas deferens and 

 the testes become smaller, shrivelled, and translucent. In Danais 

 archippus, Papilio cresphontes, and in Acronycta (sp.?) the testes, which 

 are paired in the larval stage, during the pupal stage become closely 

 applied to each other along the midline and form a single spheroidal 

 body, colored almost royal purple in D. archippus due to the pigment 

 of the surrounding epithelial coat. In D. archippus (summer brood) the 

 testes contained developed spermatozoa six days after pupation, the 

 time of pupal development being from eleven to fourteen days. In 

 moths the rate of development varies with the species. Some S. 

 cecropia and A. io kept in the laboratory became imagoes in January, 

 while C. promethea under similar conditions shows much greater retar- 

 dation. Promethea fixed in February showed a few first maturation 

 divisions and then came a long period when from March to May devel- 

 opment of the spermatozoa did not proceed farther than the spermatids. 

 The testes of the saturnids are kidney-shaped, tinged the faintest yellow 

 and divided into four lobes ; they are surrounded by a layer of con- 

 necting tissue, which forms partitions between the lobes and between 

 the cysts. The cells are arranged in the order of their development, from 

 the periphery inward: the extreme anterior end of the testis until late 

 in development is occupied by the primordial germ cells — the sperma- 



