152 



rior with tlie greatest pertinacity ; and I have been afraid of 

 injuring it by using too much force. The cocoon sent to mc by 

 Dr. Melsheimer, from which all the moths accompanying it 

 had escaped, contains the remains of the chrysalis ; both ends 

 were stopped by little flat lids of brownish silk of the thickness 

 and firmness of cartridge paper ; one of these lids remained 

 fixed, the other had been pushed off by the moth, but was still 

 attached by some threads. On the middle of the edges of the 

 six dorsal segments, the chrysalid had a transverse row of little 

 teeth, which could be shut down into corresponding cavities on 

 the top of the contiguous segment, forming six pairs of nippers, 

 which were undoubtedly intended to enable the chrysalis to 

 advance in its cocoon, and to take a firm hold when pushing off 

 the lid. The tail is blunt, with six minute points. The form 

 of the caterpillar and the structure of its cocoon are very dif- 

 ferent from those of Oiketicus and Psyche, and the moths, both 

 sexes of which are perfect and furnished with wings, and dif- 

 fer only in the narrower pectinations of the antennse of the 

 female, are not referable either to Oiketicus or Psyche. I 

 therefore propose to call the genus Saccophora, and the species 

 Melsheimeri. Will not this singular and interestino; insect 

 remove some of your difliculties respecting the transition from 

 Psyche to Bomhyx ? It may be that it is allied to some of the 

 Notodontiadce ; but I want several genera, such as Stcmropus, 

 Ptilophora, Chaonia and Peridca, to compare with it. [This 

 letter was published by Doubleday, with figures, in Newman's 

 Entomologist, pp. 99-101.] 



HARRIS TO DOUBLEDAY. 



Cambridge, Oct. 8, 1840. 



You will recollect I suggested that tlie Bonihyccs may be 

 resolved into two groups of equal value, true spinners, and im- 

 perfect spinners. At the head of each must stand the Attaci 



