144 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



ACQUIRED LARVAL CHARACTERS. 



The two subtlorsal yellowish lonjiitiuliiial stripes ]irobab]y apjiear at tiie eud of the second stage. 

 In Stage III the whitish bloom appears. In Stage IV the suiaiial plate is edged Avith yellow. 



This is, next to Gluphixia, the siinidest, least specialized Notodontian larva; more so than 

 that of Lophodonfa. The body is without tubercles or hnmps; the piliferous warts are minute and 

 the simplest markings are colorational, i. e., two yellowish subdorsal bands, with no spots. In the 

 Notodontians the subdorsal lines are the first to ajipear, before the lateral ones. 



The following is a copy of an article entitled "The number of larval stages in the genus 

 Nadata," by Mr. Harrison G. Dyar, Psyche, October, 1^92, which we rejjroduce, as it gives a full 

 account of the transformations of this species in California, and contains interesting' notes on the 

 habits: 



111 Psyche, recently, I expressed the ojiiuiou tliiit species i)( XmJata had more than six larval stayx'S, which was 

 founded on certain iiieasiirem^uts made from Xadata yibhosa. I have not since ohtained this species iu the early 

 stages, ' bnt have bred another from the egg, which is X. oreijonensis Cntl. In this species, the number of stages 

 appears to be normally six; but two individuals carefully bred iu confinement and two bred in the open air had but 

 five stages, while another specimen, less carefully reared iu confinement beside another bred in the open air on its 

 growing food plant under a net exhibited six stages, but not the normal ones. All the larvse appeared to omit the 

 normal seoond stage, even those that had six stages. These latter inserted an extra stage between the fourth aud 

 fifth, not differing in markings from the fourth, as will be seen in what follows. The growth during the first stage 

 was very great, out of all proportion to the subsequent growth, and, jirevious to molting, the new bead, in process 

 of formation behind the old one, caused au enormous projection of the body. 



The calculated normal series for the widths of head stands as follows: I, 0.7'J [II. 1.13] ; III. '.<)2: IV, 2.31: V, 

 3.3; VI, '1.7 mm.; ratio. 0.70 mm. 



From the larva' that had live st.agrs I obtained the following measurements: First, 0. ".'5; second, 1.. 55; third. 

 2.35; fourth, 3.3; fifth, 4.7 mm. 



From those that had six stages — first exiiinple: First, — ;-' second, 1.4; third, 2.2; fourth, 2.7; fifth, 3.2; sixth, 

 .— mm.'- Second example: First, — ;- second, 1.5; third, 2.3; fourth. 2.8; fifth, 3.7; sixth, 4.8 mm. 



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 iu 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 

 present a good series with the ratio 0.77, aud, jndging from these stages only, it would certainly be infeired that 

 the species h.ad eight larval stages, * with the following series of widths of head (calculated) : 0.77, 1.0, 1.3, 1.7, 2.2, 

 2.8, 3.7, 4:8 mm; ratio, 0.77 ihm. Compare with this the last four measurements of the second example. 



The species of Xadata, then, jiresent examples of variation in the number of larval st.iges, as well as an 

 abnormal development. 



It is probable that Kilema alhicosta acts in a similar though less pronounced manner. '' 



The following descriptions apply to the species of Nadat.a that is common in the Yosemite Valley, California. 



'Miss Soule has recently written the life history of X. gibbosa (Psyche, v. 6, 197) and found five stages, as did 

 also Dr. Riley (see 5th Kept. U. S. Ent. Com., 1890). Unfortunately, Miss Soule has given no measurements of the 

 head, but she has given the length of the larva in all its stiiges, and the numbers she gives correspond well with a 

 series derived with the ratio 0.60. This does not corroborate my observations (on X. orepvneiisis), as to do so a stage 

 should appear lacking between .Stages I and II, provided that the measurements were made at the first of each stage. 

 Miss Soule's figures .are 3. 16 (^19), J (^.25), A (^.50), f ( = .75), and 1^- ( = 1.25) inches, while the calculated series 

 would be .16, .27, .45, .75, 1.25 inches, thus showing no g>ap in the series anywhere. To suit my observations the 

 newly hatched larva should have measured 0.10 inch instead of 0.16 inch. Miss Soule says "not quite i% inches," 

 which is certainly nearer 0.16 than 0.10, as the latter would be not quite J inch. 



But I do not think the length of the larva is a reliable measurement to take, as it is subject to great change 

 throughout the stage, and, even if taken as nearly as possible at the same time in each stage, is subject to inaccu- 

 racies through the expansion or contraction of the larval segments. Moreover, it takes no account of the growth 

 during either the first or the last stage, according as the measurements are made at the end or beginning of each 

 ptage, and I should hesitate to assume that the growth was always strictly proportional. In fact, I believe that 

 iu Nadata it is not so, for double growth seems to take jilace in the first stage. 



The measurement of tlio width of hi^ad is opeu to none of the above objections and possesses besides several 

 advantages not shown by measurements of the len.gtb of the larva. 



-Measurement not recorded. 



•'This larva died before molting the last time. 



■I From similar measurements made in the case of A', ijibhoan, 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. 



■■^The series of widths of head as observed by me for Edema alhicosta were 0.40, 0.70, 1.30, 1.7, 2.,3, 3.2, and I have 

 twice attempted in the p.ages of Psyche to m.ake them tit a series iu regular geometrical progression, but without 



