144 MEMOIRS or TlIK NATIONAL ACADK.AIY OF SCIENCES. 



ACl.UIKKll LAUYAI. ( 11 A K ACTEKS. 



Tbetwo subdorsal yellowish loiiiiitndiiuil stripes i)r«>l);il)l\- n]i|i(';ir at tiie cini of tlie second sta.so. 

 In Stajic III tlic wliitisli Vjlnoni ai)iK'ars. In Stai;'e IV the siiranal jilate is edf;ed with yellow. 



Tliis is, next to (llKpliinia, t\[0, simplest, least specialized Notodontian larva; iiioie so tlian 

 thatof Lophotlontn. The body is without tubercles or huini)S; the ])iliferous warts are minute and 

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

 Notodontians tlie subdorsal lines are the lirst to appear, before the lateral ones. 



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

 Nadata," by Mr. Harrison G. Dyar, Psyche, October, 1892, which we rejiroduce, as it gives a full 

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

 habits: 



In I'syclie, recently, I expressed the opinion tliat species of .V(U?«7a had more than six larviil stajfes, which was 

 fonniled on certain nieasureni ^nts made troiii Xadiila <jihhi»>a. I liave not since obt.-iined this sjiecies iu the early 

 (itages, ' hnt have bred another from the (\i{j;, whicli is ^V. oreijoni-nsis liiitl. In this 8))ecies, the unmber of stages 

 appears to be normally six; but two individuals carefully bred in eonfineiiient and two bred in the o]hu air had but 

 live stages, while another specimen, less carefully reared in conlinement beside another bred in the o]>en air on its 

 growing food plant nuder .a net exhibited six stages, but not tlio normal ones. All the larvae appeared to omit the 

 normal second stage, even those that had six stages. Tliese latter inserte<l an extra stage between the fourth and 

 fifth, not differing in markings from the fourth, as will be seen iu what follows. The growth dnring the lirst stage 

 was very great, out of all proportion to the subsccinent growth, and, ])revious to molting, the new head, in iirocess 

 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!' [11. l.lo] ; 111. i.ilL': I\'. 2.31; V, 

 3.3; VI, 4.7 mm.; ratio. 0.70 mm. 



From the larva' that had live stages I obtained the following measurements: First, 0.7."! ; second, !..")."> ; third, 

 2.3i5; fourth, 3.3; fifth, 4.7 mm. 



From those that had six stages — lirst example: First. — ;■ second, 1.4; third. 2.2; fourth. 2.7; tilth. 3.2: sixth, 

 ■ — mm.^ Second example: First, — ;- second, 1..5; third, 2.3; fourth, 2.S; tilth, 3.7; sixth, 4.8 mm. 



It will be seen that in the first example an e.xtra st.age occurred between the normal Stages IV and \'. and this 

 is verified by tlie changes in markings; for iu those that had live stages, the markings changed in tlm 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, and, .judging from these stages only, it would certainly be inferred that 

 the species had 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 mm. Compare with this the last four measurements of the second example. 



The s]iecies of Nadata, then, jiresent examples of variation in the number of larval stages, as well as an 

 abnormal develojiment. 



It is jirobable that Edema uUiirosIa acts in a, similar though less pnmounced m.'inuer.'^ 



The following descriptions apply to the species of Nadata that is counnon iu the Yosemite Valley, California. 



'Miss Soule has recently written the life history of X. r/ihhosa (Psyche, v. 6, 197) and found five 8tage.s, as did 

 also Dr. Hiley (see 5th Kept. V. S. Knt. Com., 18110) . Unfortunately, Miss Soule has given no measurements of the 

 head, but she has given the length of the larva iu all its stages, and the numbers she gives correspond W(dl with a 

 series deriveil with the ratio 0.60. This does not corroborate my ob.servations (on -V. oregovcimis), 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 8oulc.'s figures are 3.16 (=19), i ( = .25), i ( = .50), f ( = .75), and 1^ (^1.25) inches, while the calculated series 

 would bo .16, .27, .45, .75, 1.25 inches, thus showing no gap 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 th;oi 0.10, .as the latter would be not quite | inch. 



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

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

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

 during either the lirst or the last stage, according as the measurements are made at the end or beginning of eai-h 

 stage, and I should hesitate to assume that the growth was always strictly projiortional. In fact. 1 believe that 

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



The measun'im^nt of the width of head is open to none of the above objections and i)ossesses besides several 

 advantages not shown by measurements of the length of the larva. 



-Measurement not recorded. 



^This larva died before molting the last time. 



'From similar measurements made iu the case of X i/ibbosa, I inferred that that species had more than six 

 Dtages (see Psyche, v. 6, p. 147), but this inference is not justified by the facts. It will bo found, however; to hiive 

 Dccasion;iIly .as many as six stages. 



■''The series of widths of head as observed by nui for Eilrmn alhiroxln were 0.40, 0.70, 1.30, 1.7, 2.3, 3.2, and I have 

 twice attempted In the pages of Psyche to make tluim fit :i series iu regular geometrical {jrogression, but without 



