PROCEEDINGS, 1918 65 



now become apparent, in the development of "dorsal tufts" on 

 the first four abdominal segments, which now begins to occur, 

 and of another dorsal tuft, the "caudal tuft," on the eighth ab- 

 dominal, from the merging of the two dorsal tufts of that seg- 

 ment. 



Third Instar. This instar differs from the preceding in 

 the greater development of the hair pencils on the first thoracic 

 and last abdominal segments. The hair pencils are composed 

 of long plumed black hairs of varying lengths. The thoracic 

 pair are 1 m. m.-2 m. m., the abdominal 1 m. m.-1.5 m. m. in 

 length. The dorsal tufts are composed of black mingled with 

 a few white hairs; the caudal tuft is of thick black plumed hairs, 

 similar to those of the hair pencils and slightly larger than the 

 white tufts of row II, which support it on either side. Length, 

 5.6 m. m. Head, 1.05 m. tn.-l.15 m. m. in width. In other 

 respects this instar resembles the preceding. 



Fourth Instar. Very similar to preceding instar. Spin- 

 iform black hairs apparent among the white tufts on body 

 warts. The tufts of the subspiracular row (V) now bear a 

 single long, black, central plumed hair in addition to the others. 

 Hair pencils of first thoracic segment, 4 m. m.-5 m. m., of last 

 abdominal segment 3 m. m.-4 m. m. Caudal tuft, 1 m. m.- 

 1.5 m. m. long. Length of body, 8 m. m.-lO m. m.; head 1.48 

 m. m. 1.51 m. m. in length. 



Fifth Instar. Differs from preceding instars chiefly in 

 size. In some cases there are two of the central black plumed 

 hairs in the tufts of the subspiracular row (IV) on the first ab- 

 dominal segment. Hair pencils of first thoracic segments, 5 

 m. m.-6 m. m. long. Length of body, 12 m. m.-14 m. m. Head, 

 2 m. m.-2.2 m. m. 



Sixth Instar. Differs but little from preceding instar. 

 Dorsal tubercles squarely cut, the first mouse color, the re- 

 mainder whitish grey in most specimens; but there is some var- 

 iation in this respect. All specimens examined had two of the 

 central plumed black hairs among the white ones of the sub- 

 spiracular row (IV), and in some cases there were three. Lat- 

 eral hair pencils of first thoracic segment, 7 m. m.-8 m. m., of 

 the last abdominal segment 6 m. m.-7 m. m. long. Length of 

 body, 15 m. m.-17 m. m.; head, 2.34 m. m.-2.56 m. m. in length. 



Seventh Instar. Warts, as in preceding instars, with tufts 

 of plumed white hair, among which scattering spiniform black 

 hairs are interspersed. Dorsal tufts, squarely cut, consisting 

 of brownish hairs usually plentifully intermingled with white. 

 The greatest variation exists in this instar in the number and 



