( XXV ) 



complete row upon all or nearly all the segments ; frequently a 

 double row occurs upon each side of the caterpillar. Generally 

 the proportion of individuals in a brood bearing the character 

 is small ; Prof. Weissmann observed a brood of ninety through- 

 out its ontogeny, in which there was but one spotted. Not- 

 withstanding these points of irregularity, there is apparently 

 a regular course of development in relation to the segments 

 that is distinctly traceable. This is shown in a series of 

 analytical tables, in which the value of the spots is reduced 

 to numerical equivalents. Upon twenty-two specimens of 

 such larvse (preserved) being submitted to close analysis, the 

 order of development upon the segments is ascertained to be 

 as follows : — 



Dorsal row . . . 3, 7, 4, II., 5, 1, 6, 2, III., I., 8. 

 Spiracular row . . 4, 3, 5, II., 7, 6, 2, 8, 1, III., I. 



The dorsal row is the more important series, and in the 

 above summary it is thus shown that the development 

 originates upon the 3rd abdominal segment. This point is 

 well borne out by instances in which it is the only segment 

 that bears the spots, and the experience of Dr. Weissmann is 

 in exact agreement with this evidence. The next segment 

 upon which it appears is the 7th abdominal, the 4th being in 

 almost equal relation to that segment ; then follows the 2nd 

 thoracic segment (the three thoracic segments are distin- 

 guished by roman numerals) ; then the 5th abdominal, &c, 

 as tabulated. 



Another peculiarity shown in the tables is that there is a 

 tendency towards a higher development on the left side than 

 on the right. There are individuals which reverse this cha- 

 racter slightly, but the tendency in the aggregate is in favour 

 of the left side. It is not easy to imagine any cause for this 

 inequality. 



Mr. White said he took exception to Weissmann's theory that 

 the spots form the nucleus of the coloured border to the white 

 stripes of the allied Sphinx ligustri, which he considers is not 

 supported even by his own evidence ; for, as he himself states, 

 the spots upon Smerinthus, when they occur, never develop 

 beyond the spot state, while the stripes of Sphinx appear 



PROC. ENT. SOC. LOND., III., 1887. F 



