338 



PSYCHE. 



[October iSc)?- 



It will be seen that in the first example 

 an extra stage occurred between the 

 normal stages IV and V, and this is 

 verified by the changes in markings ; 

 for in those that had five stages, the 

 markings changed in the fourth stage, 

 while in this, the fourth stage was like 

 the third and the change did not occur 

 till the fifth stage.* 



In the second example the fifth stage 

 was abnormally large, so much so that 

 the last four stages, in this case, pre- 

 sent a good series with the ratio .77. 

 and, judging from these stages only, it 

 would certainly be inferred that the 

 species had eight larval stages, f with 

 the following series of widths of head : — 

 calculated — .77, 1.0,1.3, 1.7, 2.2, 2.8, 

 3.7, 4.S, mm., ratio .77. Compare with 

 this the last four measurements of the 

 second example. 



The species of Nadata, then, present 

 examples of variation in the number of 

 larval stages, as well as an abnormal 

 development. 



It is probable that Edema albicosta 

 acts in a similar, though less pro- 



* In this connection I would like to call attention to 

 ray note on Spilosoma latipennis (Ent. news, v. 2, p. 

 115) where it will be seen an extra stage occurred be- 

 tween normal stages VIII and IX, not differing in 

 markings from the stage before it, exactly as in the 

 present instance. These cases are not analogous with 

 such as are exhibited in Orgyia where an extra stage 

 occurs in 9 larvae, for the latter takes place to afford 

 an increase in size. In the present instances the larvae 

 with the extra stage are no larger than those with the 

 normal number, and the stage is interpolated before 

 the final stage instead of occurring after it. 



t From similar measurements made in the case of 

 N. gibbosa, I inferred that that species had more than 

 six stages (see Psyche, v. 6, p. 147), but this inference 

 is not justified by the facts. It will be found, however' 

 to have occasionally as many as six stages. 



nounced manner. \ 



The following descriptions apply to 

 the species of Nadata that is common: 

 in the Yosemite Valley, Cal. 



Nadata okegonensis Butler. § 



1SS1 — Butler, Ann. and mag. nat. 

 hist., p. 317. 



behrensii Hy. Edwards. 



1SS5 — Hy. Edw., Ent. Amer., i, 49. 



Egg. Rather more than hemispherical, 

 the base flattened ; smooth, not shiny, white 

 with a yellowish tinge; diameter 1.2 nun. 

 Under a microscope the surface is seen to be 

 covered with very slight, obscure, rounded 

 depressions, but, in fact, almost smooth. 



Laid singly on the under side of the leaves 

 of its food plants in early summer. 



\ The series of widths of head as observed by me for 

 Edema albicosta were .40, .70, 1.30, 1.7, 2.3, 3.2, and I 

 have twice attempted in the pages of Psyche to make 

 them fit a series in regular geometrical progression, 

 but without marked success. A series calculated with 

 the ratio .55 would give — .41, .75, 1.27, 2.30, 4.3, and one 

 with the ratio .73 or thereabout would interpolate a 

 term between each one and give .41, .55, .75, .96, 1.27, 

 1.7,2.3,3.15,4.3. Thus it might be considered either 

 that the species normally had eight stages (ratio .73) 

 and omitted the second and fourth normal stages, 

 or that it had normally five stages (ratio -55), 

 but interpolated a stage between the third and fourth 

 normal stages, and reduced the measurement in 

 the last stage to correspond with the ratio between those 

 that immediately preceded it. The latter seems the 

 more probable, but the fact is that the growth of the 

 head at the first and second moults is double what it is 

 at the third, fourth and fifth. It is a curious case. 



§ This was described as a variety of N. doubledayi 

 Pack.; but Mr. Butler writes me under date of June 30, 

 1S92 — "The types . . . have pale creamy buff-colored 

 palpi; quite uniform in tint . . . if there is a brown 

 line above it must be on the second joint, but I do not 

 think there is one . . . looking- at the moth without a 

 lens you would say the fringe was dark ferruginous on 

 primaries . . . and white tipped on interspaces." 

 These are the characters used to separate N. gibbosa 

 from D. doubledayi in Dr. Packard's description, 

 and Mr. Butler's words show that his form is not a 

 variety of A 7 ', doubledayi, but the same as Hy. Edward's 

 JV. behrensii. 



