Chapter XXIII: Introduction (3)

[6] [Eng. ed. I learn by a written communication from Dr. Speyer that two Geometræ, _Selenia Tetralunaria_ and _S. Illunaria_ Hüb., are seasonally dimorphic. In both species the winter form is much larger and darker.] [_Selenia Lunaria_, _S. Illustraria_, and some species of _Ephyra_ (_E. Punctaria_ and _E. Omicronaria_) are likewise seasonally dimorphic. For remarks on the case of _S. Illustraria_ see Dr. Knaggs in Ent. Mo. Mag., vol. iii. p. 238, and p. 256. Some observations on _E. Punctaria_ were communicated to the Entomological Society of London by Professor Westwood in 1877, on the authority of Mr. B. G. Cole. See Proc. Ent. Soc. 1877, pp. vi, vii. R.M.]

[7] [In 1860 Andrew Murray directed attention to the disguising colours of species which, like the Alpine hare, stoat, and ptarmigan, undergo seasonal variation of colour. See a paper “On the Disguises of Nature, being an inquiry into the laws which regulate external form and colour in plants and animals.” Edinb. New Phil. Journ., Jan. 1860. In 1873 I attempted to show that these and other cases of “variable protective colouring” could be fairly attributed to natural selection. See Proc. Zoo. Soc., Feb. 4th, 1873, pp. 153-162. R.M.]

[8] [A phenomenon somewhat analogous to seasonal change of protecting colour does occur in some Lepidoptera, only the change, instead of occurring in the same individual, is displayed by the successive individuals of the same brood. See Dr. Wallace on _Bombyx Cynthia_, Trans. Ent. Soc. Vol. v. p. 485. R.M.]

[9] “Über den Einfluss der Isolirung auf die Artbildung.” Leipzig, 1872, pp. 55-62.

[10] [Mr. A. R. Wallace maintains that the obscurely coloured females of those butterflies which possess brightly coloured males have been rendered inconspicuous by natural selection, owing to the greater need of protection by the former sex. See “Contributions to the Theory of Natural Selection,” London, 1870, pp. 112-114. It is now generally admitted that the underside of butterflies has undergone protectional adaptation; and many cases of local variation in the colour of the underside of the wings, in accordance with the nature of the soil, &c., are known. See, for instance, Mr. D. G. Rutherford on the colour-varieties of _Aterica Meleagris_ (Proc. Ent. Soc. 1878, p. xlii.), and Mr. J. Jenner Weir on a similar phenomenon in _Hipparchia Semele_ (_loc. cit._ p. xlix.) R.M.]

[11] [The fact that moths which, like the Geometræ, rest by day with the wings spread out, are protectively marked on the _upper_ side, fully corroborates this statement. R.M.]

[12] “Über die Einwirkung verschiedener, während der Entwicklungsperioden angewendeter Wärmegrade auf die Färbung und Zeichnung der Schmetterlinge.” A communication to the Society of Natural Science of Steiermark, 1864.

[13] See Exp. 9, Appendix I.

[14] See Exp. 11, Appendix I.

[15] See Exps. 4, 9, and 11, Appendix I.

[16] It seems to me very necessary to have a word expressing whether a species produces one, two, or more generations in the year, and I have therefore coined the expression _mono-_, _di-_, and _polygoneutic_ from γονεύω, I produce.

[17] [Eng. ed. In the German edition, which appeared in 1874, I was not able to support this hypothesis by geographical data, and could then only ask the question “whether in the most northern portion of its area of distribution, appears in two or only in one generation?” This question is now answered by the Swedish Expedition to the Yenisei in 1876. Herr Philipp Trybom, one of the members of this expedition, observed _A. Levana_ at the end of June and beginning of July, in the middle of Yenisei, in 60°-63° N. (Dagfjärilar från Yenisei in Översigt ap k. Vertensk. Akad. Förhandlingon, 1877, No. 6.) Trybom found _Levana_ at Yenisk on June 23rd, at Worogova (61° 5´) on July 3rd, at Asinova (61° 25´) on July 4th, at Insarowa (62° 5´) on July 7th, and at Alinskaja (63° 25´) on July 9th. The butterflies were especially abundant at the beginning of June, and were all of the typical _Levana_ form. Trybom expressly states, “we did not find a single specimen which differed perceptibly from Weismann’s Figs. 1 and 2 (‘Saison-Dimorphismus’ Taf. I.).”

The Swedish expedition soon left the Yenisei, and consequently was not able to decide by observations whether a second generation possessing the _Prorsa_ form appeared later in the summer. Nevertheless, it may be stated with great probability that this is not the case. The districts in which _Levana_ occurs on the Yenisei have about the same isotherm as Archangel or Haparanda, and therefore the same summer temperature. Dr. Staudinger, whose views I solicited, writes to me:--“In Finnmark (about 67° N.) I observed no species with two generations; even _Polyommatus Phlæas_, which occurs there, and which in Germany has always two, and in the south, perhaps, three generations, in Finnmark has only one generation. A second generation would be impossible, and this would also be the case with _Levana_ in the middle of Yenisei. I certainly have _Levana_ and _Prorsa_ from the middle of Amur, but _Levana_ flies there at the end of May, and the summers are very warm.” The middle of Amur lies, moreover, in 50° N. lat., and therefore 10°-13° south of the districts of the Yenisei mentioned.

It must thus be certainly admitted that on the Yenisei _A. Levana_ occurs only in the _Levana_ form, and that consequently this species is at the present time, in the northernmost portion of its area of distribution, in the same condition as that in which I conceive it to have been in mid Europe during the glacial period. It would be of the greatest interest to make experiments in breeding with this single-brooded _Levana_ from the Yenisei, i.e., to attempt to change its offspring into the _Prorsa_ form by the action of a high temperature. If this could not be accomplished it would furnish a confirmation of my hypothesis than which nothing more rigorous could be desired.]

[18] See Exp. 10, Appendix I.

[19] When Dorfmeister remarks that hibernating pupæ which, at an early stage “were taken for development into a room, or not exposed to any cold, gave dwarfed, weakly and crippled,” or otherwise damaged butterflies, this is entirely attributable to the fact that this able entomologist had neglected to supply the necessary moisture to the warm air. By keeping pupæ over water I have always obtained very fine butterflies.

[20] [For other remarkable cases of sexual dimorphism (not _antigeny_ in the sense used by Mr. S. H. Scudder, Proc. Amer. Acad., vol. xii. 1877, pp. 150-158) see Wallace “On the Phenomena of Variation and Geographical Distribution, as illustrated by the Papilionidæ of the Malayan Region,” Trans. Linn. Soc., vol. xxv. 1865, pp. 5-10. R.M.]

[21] [Eng. ed. Dimorphism of this kind has since been made known: the North American _Limenitis Artemis_ and _L. Proserpina_ are not two species, as was formerly believed, but only one. Edwards bred both forms from eggs of _Proserpina_. Both are single-brooded, and both have males and females. The two forms fly together, but _L. Artemis_ is much more widely distributed, and more abundant than _L. Proserpina_. See “Butterflies of North America,” vol. ii.]

[22] [Eng. ed. Edwards has since proved experimentally that by the application of ice a large proportion of the pupæ do indeed give rise to the var. _Telamonides_. He bred from eggs of _Telamonides_ 122 pupæ, which, under natural conditions, would nearly all have given the var. _Marcellus_. After two months’ exposure to the low temperature there emerged from August 24th to October 16th, fifty butterflies, viz. twenty-two _Telamonides_, one intermediate form between _Telamonides_ and _Walshii_, eight intermediate forms between _Telamonides_ and _Marcellus_ more nearly related to the former, six intermediate forms between _Telamonides_ and _Marcellus_, but more closely resembling the latter, and thirteen _Marcellus_. Through various mishaps the action of the ice was not complete and equal. See the “Canadian Entomologist,” 1875, p. 228. In the newly discovered case of _Phyciodes Tharos_ also, Edwards has succeeded in causing the brood from the winter form to revert, by the application of ice to this same form. See Appendix II. for a _résumé_ of Edwards’ experiments upon both _Papilio Ajax_ and _Phyciodes Tharos_. R.M.]

[23] Thus from eggs of _Walshii_, laid on April 10th, Edwards obtained, after a pupal period of fourteen days, from the 1st to the 6th of June, fifty-eight butterflies of the form _Marcellus_, one of _Walshii_, and one of _Telamonides_.

[24] [The word ‘Amixie,’ from the Greek ἀμιξία, was first adopted by the author to express the idea of the prevention of crossing by isolation in his essay “Über den Einfluss der Isolirung auf die Artbildung,” Leipzig, 1872, p. 49. R.M.]

[25] [Eng. ed. In 1844, Boisduval maintained this relationship of the two forms. See Speyer’s “Geographische Verbreit. d. Schmetterl.,” i. p. 455.]

[26] According to a written communication from Dr. Staudinger, the female _Bryoniæ_ from Lapland are never so dusky as is commonly the case in the Alps, but they often have, on the other hand, a yellow instead of a white ground-colour. In the Alps, yellow specimens are not uncommon, and in the Jura are even the rule.

[27] [According to W. F. Kirby (Syn. Cat. Diurn. Lepidop.), the species is almost cosmopolitan, occurring, as well as throughout Europe, in Northern India (var. _Timeus_), Shanghai (var. _Chinensis_), Abyssinia (var. _Pseudophlæas_), Massachusetts (var. _Americana_), and California (var. _Hypophlæas_). In a long series from Northern India, in my own collection, all the specimens are extremely dark, the males being almost black. R.M.]

[28] [Eng. ed. From a written communication from Dr. Speyer, it appears that also in Germany there is a small difference between the two generations. The German summer brood has likewise more black on the upper side, although seldom so much as the South European summer brood.]

[29] [Assuming that in all butterflies similar colours are produced by the same chemical compounds. R.M.]

[30] [Mr. H. W. Bates mentions instances of local variation in colour affecting many distinct species in the same district in his memoir “On the Lepidoptera of the Amazon Valley;” Trans. Linn. Soc., vol. xxiii. Mr. A. R. Wallace also has brought together a large number of cases of variation in colour according to distribution, in his address to the biological section of the British Association at Glasgow in 1876. See “Brit. Assoc. Report,” 1876, pp. 100-110. For observations on the change of colour in British Lepidoptera according to distribution see papers by Mr. E. Birchall in “Ent. Mo. Mag.,” Nov., 1876, and by Dr. F. Buchanan White, “Ent. Mo. Mag.,” Dec., 1876. The colour variations in all these cases are of course not _protective_ as in the well-known case of _Gnophos obscurata_, &c. R.M.]

[31] See Figs. 10 and 14, 11 and 15, Plate I.

[32] “On the Origin and Metamorphoses of Insects,” London, 1874.

[33] I at first thought of designating the two forms of cyclical or homochronic heredity as ontogenetic- and phyletic-cyclical heredity. The former would certainly be correct; the latter would be also applicable to alternation of generation (in which actually two or more phyletic stages alternate with each other) but not to all those cases which I attribute to heterogenesis, in which, as with seasonal dimorphism, a series of generations of _the same_ phyletic stage constitute the point of departure.

[34] When Meyer-Dürr, who is otherwise very accurate, states in his “Verzeichniss der Schmetterlinge der Schweiz,” (1852, p. 207), that the winter and summer generations of _P. Ægeria_ differ to a small extent in the contour of the wings and in marking, he has committed an error. The characters which this author attributes to the summer form are much more applicable to the female sex. There exists in this species a trifling sexual dimorphism, but no seasonal dimorphism.

[35] P. C. Zeller, “Bemerkungen über die auf einer Reise nach Italien und Sicilien gesammelten Schmetterlingsarten.” Isis, 1847, ii.-xii.

[36] “Isoporien der europäischen Tagfalter.” Stuttgart, 1873.

[37] [Trans. Linn. Soc., vol. xxv. 1865, p. 9. R.M.]

[38] It is certainly preferable to make use of the expression “metagenesis” in this special sense instead of introducing a new one. As a general designation, comprehending metagenesis and heterogenesis, there will then remain the expression “alternation of generation,” if one does not prefer to say “cyclical propagation.” The latter may be well used in contradistinction to “metamorphosis.”

[39] _Loc. cit._ chap. iv.

[40] The idea that alternation of generation is derived from polymorphism (not the reverse, as usually happens; i.e. polymorphism from alternation of generation) is not new, as I find whilst correcting the final proof. Semper has already expressed it at the conclusion of his interesting memoir, “Über Generationswechsel bei Steinkorallen,” &c. See “Zeitschrift f. wiss. Zool.” vol. xxii. 1872.

[41] See my essay “Über den Einfluss der Isolirung auf die Artbildung.” Leipzig, 1872.

[42] [In the case of monogoneutic species which, by artificial ‘forcing,’ have been made to give two generations in the year, it has generally been found that the reproductive system has been imperfectly developed in the second brood. A minute anatomical investigation of the sexual organs in the two broods of seasonally dimorphic insects would be of great interest, and might lead to important results. R.M.]

[43] “Grundzüge der Zoologie.” 2nd ed. Leipzig, 1872. Introduction.

[44] With reference to this subject, see the discussion by the Belgian Entomological Society, Brussels, 1873.

[45] P. E. Müller, “Bidrag til Cladocerners Fortplantingshistorie,” 1868.

[46] Sars, in “Förhandlinger i Videnskabs Selskabet i Christiania,” 1873, part i.

[47] [Eng. ed. Recent researches on alternation of generation in the Daphniacea have convinced me that _direct_ action of external conditions does not in these cases come into consideration, but only _indirect_ action.]

[48] See my memoir, “Über Bau und Lebenserscheinungen der _Leptodora hyalina_,” Zeitschrift f. wiss. Zool., vol. xxiv. part 3, 1874.

[49] Stettin. entom. Zeit., vol. xviii. p. 83, 1857.

[50] Compt. Rend., vol. lxxvii. p. 1164, 1873.

[51] [“Accidental” in the sense of our being in ignorance of the laws of variation, as so frequently insisted upon by Darwin. R.M.]

[52] [Eng. ed. Since this was written I have studied the ornamental colours of the _Daphniidæ_; and, as a result, I no longer doubt that sexual selection plays a very important part in the marking and colouring of butterflies. I by no means exclude both transforming factors, however; it is quite conceivable, on the contrary, that a change produced directly by climate may be still further increased by sexual selection. The above given case of _Polyommatus Phlæas_ may perhaps be explained in this manner. That sexual selection plays a part in butterflies, is proved above all by the odoriferous scales and tufts of the males discovered by Fritz Müller.] [For remarks on the odours emitted by butterflies and moths, see Fritz Müller in “Jena. Zeit. f. Naturwissen.,” vol. xi. p. 99; also “Notes on Brazilian Entomology,” Trans. Ent. Soc. 1878, p. 211. The odoriferous organs of the female _Heliconinæ_ are fully described in a paper in “Zeit. f. Wissen. Zool.,” vol. xxx. p. 167. The position of the scent-tufts in the sphinx-moths is shown in Proc. Entom. Soc. 1878, p. ii. Many British moths, such as _Phlogophora meticulosa_, _Cosmia trapezina_, &c. &c., have tufts in a similar position. The fans on the feet of _Acidalia bisetata_, _Herminia barbalis_, _H. tarsipennalis_, &c., are also probably scent organs. A large moth from Jamaica, well known to possess a powerful odour when alive (_Erebus odorus_ Linn.), has great scent-tufts on the hind legs. For the application of the theory of sexual selection to butterflies, see, in addition, to Darwin’s “Descent of Man,” Fritz Müller in “Kosmos,” vol. ii. p. 42; also for January, 1879, p. 285; and Darwin in “Nature,” vol. xxi. January 8th, 1880, p. 237. R.M.]

[53] Nägeli, “Entstehung und Begriff der naturhistorischen Art,” Munich, 1865, p. 25. The author interprets the facts above quoted in a quite opposite sense, but this is obviously erroneous.

[54] See my essay, “Über den Einfluss der Isolirung auf die Artbildung.” Leipzig, 1872.

[55] [Eng. ed. In the summer of 1877, Dr. Hilgendorf again investigated the Steinheim fossil shells, and found his former statements to be completely confirmed. At the meeting of the German Naturalists and Physicists at Munich, in 1877, he exhibited numerous preparations, which left no doubt that the chief results of his first research were correct, and that there have been deposited a series of successively derived species together with their connecting intermediate forms.]

[56] See my essay, “Über die Berechtigung der Darwin’schen Theorie.” Leipzig, 1868.

[57] I expressly insist upon this here, because the notice of Askenasy’s thoughtful essay which I gave in the “Archiv für Anthropologie” (1873) has frequently been misunderstood.

[58] The experiments upon _Papilio Ajax_ and _Phyciodes Tharos_, described in this Appendix, were made by Mr. W. H. Edwards (see his “Butterflies of North America;” also the “Canadian Entomologist,” vol. vii. p. 228-240, and vol. ix. p. 1-10, 51-5, and 203-6); and I have added them, together with some hitherto unpublished results, to Dr. Weismann’s Essay, in order to complete the history of the subject of seasonal dimorphism up to the present time.--R.M.

[59] This is a striking illustration of the diversity of individual constitution so frequently insisted on by Dr. Weismann in the foregoing portion of this work.

[60] The reader who wishes to acquire a detailed knowledge of the different varieties of this butterfly, of which a very large number are known, must consult the plates and descriptions in Edwards’ “Butterflies of North America,” vol. ii.

[61] Mr. Edwards has shown also that _Argynnis Myrina_ can lay fertile eggs when but a few hours out of the chrysalis. Canad. Ent., September, 1876, vol. viii. No. 9.

[62] Mr. Edwards remarks that the habit of becoming lethargic is of great service to a digoneutic species in a mountain region where it is exposed to sharp changes of temperature. “If the fate of the species depended on the last larval brood of the year, and especially if the larvæ must reach a certain stage of growth before they were fitted to enter upon their hibernation, it might well happen that now and then an early frost or a tempestuous season would destroy all the larvæ of the district.”

[63] Compare this with Weismann’s remarks, pp. 19-22, and 53.

[64] See Canad. Ent., vol. ix. p. 69.

[65] Figures of the different forms of this species are given in vol. i. of Edward’s “Butterflies of North America.”

[66] Only the species of _Smerinthus_ can be made to lay eggs regularly in confinement; _Macroglossa Stellatarum_ laid a number in a large gauze-covered breeding-cage; the species of _Deilephila_ could not be induced to lay more than single ones in such a cage. From species of _Chærocampa_ also I never obtained but a few eggs, and from _Sphinx_ and _Acherontia_ never more than single ones.

[67] [Eng. ed. Since the appearance of the German edition of this work, numerous descriptions of the young stages of caterpillars have been given, but in all cases without representing the relationship of the forms.] [In the excellent figures of larvæ at various stages of growth, given in some of the more recent works on Lepidoptera, there will be found much material which may be regarded as a contribution to the field of research entered on by the author in the present essay, _i.e._ the ontogeny and comparative morphology of larval markings, although it is much to be regretted that the figures and descriptions have not been given from this point of view. In his “Butterflies of North America,” for example, W. H. Edwards figures the young as well as the adult larvæ of species of _Apatura_, _Argynnis_, _Libythea_, _Phyciodes_, _Limenitis_, _Colias_, _Papilio_, &c. Burmeister, in his recently published “Lépidoptères de la République Argentine,” figures the young stages of species of _Caligo_, _Opsiphanes_, _Callidryas_, _Philampelus_, &c. Messrs. Hellins and Buckler have figured and described the early stages of large numbers of the caterpillars of British Lepidoptera, but their figures remain unpublished. The larvæ of many of our native species belonging to the genera _Liparis_, _Tæniocampa_, _Epunda_, _Cymatophora_, _Calocampa_, &c., are dull when young, but become brightly coloured at the last moult. Such changes of colour are probably associated with some change, either in the habits or in the environment; and a careful study of the ontogenetic development of such species in connection with their life-history would furnish results of great value to the present inquiry. The same remarks apply to those _Noctuæ_ larvæ which are brightly coloured in their young stages, and become dull when adult.

Among other papers which may be considered as contributions to the present subject, I may mention the following:--In 1864 Capt. Hutton published a paper, “On the Reversion and Restoration of the Silkworm, Part II.” (Trans. Ent. Soc. 1864, p. 295), in which he describes the various stages of development of several species of _Bombycidæ_. In 1867 G. Semper published accounts of the early stages of several Sphinx-larvæ (“Beiträge zur Entwicklungsgeschichte einiger ostasiatischer Schmetterlinge,” Verhandl. k.k. Zoolog.-botan. Gesell. in Wien, vol. xvii.). The question as to the number of claspers in young _Noctuæ_ larvæ has been raised in notes by Dr. F. Buchanan White (“Ent. Mo. Mag.,” vol. v. p. 204) and B. Lockyer (“Entomologist,” 1871, p. 433). A valuable paper, “On the Embryonic Larvæ of Butterflies,” was published in 1871 by S. H. Scudder (“Ent. Mo. Mag.,” vol. viii. p. 122). For remarks on the development of the larva of _Papilio Merope_, see J. P. Mansel Weale in Trans. Ent. Soc., 1874, p. 131, and Pl. I.; also this author on the young stages of the larva of _Gynanisa Isis_, Trans. Ent. Soc., 1878, p. 184. For an account of the development of the larvæ of certain North American species of _Satyrus_, see W. H. Edwards in the “Canadian Entom.,” vol. xii. p. 21. Mr. P. H. Gosse’s recent description of the newly hatched caterpillar of _Papilio Homerus_ (Proc. Ent. Soc. 1879, p. lv), furnishes a good illustration of the value of studying the ontogeny. The natural affinities of the _Papilionidæ_ were at one time much disputed, some systematists placing this family at the head of the Lepidoptera, and others regarding them as being more closely allied to the moths. Mr. Gosse’s observation tends to confirm the latter view, now generally received by Lepidopterists, since he states that the larva in question “suggests one of the great _Saturniadæ_, such as _Samia Cecropia_.” Mr. Scudder, in the paper above referred to, adopts an analogous argument to show the close relationship between the _Papilionidæ_ and _Hesperidæ_. R.M.]

[68] [Mr. A. G. Butler has recently furnished a good illustration of the danger of classifying Lepidoptera according to the affinities of the perfect insects only, in his paper, “On the Natural Affinities of the Lepidoptera hitherto referred to the Genus _Acronycta_ of authors,” Trans. Ent. Soc. 1879, p. 313. If the author’s views are ultimately accepted, the species at present grouped under this genus will be distributed among the _Arctiidæ_, _Liparidæ_, _Notodontidæ_, and _Noctuæ_. Mr. Butler’s determination of the affinities of the species supposed to belong to the genus mentioned, is based chiefly upon a comparative examination of the larvæ, and this is far more likely to show the true blood-relationship of the species than a comparison of the perfect insects only. A study of the comparative ontogeny can alone give a final answer to this question. R.M.]

[69] [In his recent revision of the _Sphingidæ_, Mr. A. G. Butler (Trans. Zoo. Soc., vol. ix. part x.) retains Walker’s arrangement. R.M.]

[70] The deposition of black pigment may commence immediately before ecdysis.

[71] [Mr. Herbert Goss states (Proc. Ent. Soc. 1878, p. v.) that according to his experience, the green and brown varieties of _C. Porcellus_ (erroneously printed as _Elpenor_ in the passage referred to) are about equally common, the former colour not being in any way confined to young larvæ. Mr. Owen Wilson in his recent work, “The Larvæ of British Lepidoptera and their food-plants,” figures (Pl. VIII., Figs. 3 and 3a) the two forms, both apparently in the adult state. During the years 1878-79, my friend, Mr. J. Evershed, jun., took five of these full-grown larvæ in Surrey, one of these being the green variety. In order to get more statistics on this subject, I applied this year (1880) to Messrs. Davis of Dartford, who informed me that among 18-20 adult caterpillars of _Porcellus_ in their possession, there was only one green specimen. R.M.]

[72] I unite the genera _Pergesa_ and _Darapsa_ of Walk. with _Chærocampa_, Dup.; the first appears to me to be quite untenable, since it is impossible that two species, of which the caterpillars agree so completely as those of _C. Elpenor_ and _Porcellus_, can be located in different genera. _Porcellus_ indeed was referred to the genus _Pergesa_ because of its different contour of wings, an instance which distinctly shows how dangerous it is to attempt to found Lepidopterous genera without considering the caterpillars. The genus _Darapsa_ also appears to me to be of very doubtful value, and in any case requires further confirmation with respect to the larval forms.

[73] [Mr. A. G. Butler (Trans. Zoo. Soc., vol. ix., part. x., 1876) gives a list of about eighty-four species of _Chærocampa_, and sixteen of _Pergesa_, besides numerous other species belonging to several genera placed between _Chærocampa_ and _Pergesa_. Of _Darapsa_, he states “that this genus was founded upon most heterogeneous material, the first three species being referable to Hübner’s genus _Otus_, the fifth to Walker’s genus _Diodosida_, the sixth and eighth to the genus _Daphnis_ of Hübner, the seventh, ninth, and tenth to _Chærocampa_ of Duponchel; there therefore remains only the fourth species, allied to _Chærocampa_, but apparently sufficiently distinct.” The species still retained in the genus _Darapsa_ is _D. rhodocera_, Wlk., from Haiti. R.M.]

[74] [_Otus Syriacus_ of Butler’s revision. R.M.]

[75] Abbot and Smith. “The Natural History of the rarer Lepidopterous Insects of Georgia, collected from the observations of John Abbot, with the plants on which they feed.” London, 1797, 2 vols. fol.

[76] [_Otus Chœrilus_ and _O. Myron_ of Butler’s revision. R.M.]

[77] [To this group may also be added _Ampelophaga Rubiginosa_, Ménétriés, from China and Japan, the caterpillar of which, having the distinct subdorsal line without any trace of eye-spots, is figured by Butler (_loc. cit._, Pl. XCI., Fig. 4). This author also gives a figure of another species belonging to the subfamily _Chærocampinæ_ (Pl. XC., Fig. 11), viz. _Acosmeryx Anceus_, Cram., from Amboina, Java, Silhet, and S. India; the caterpillar is green, with seven oblique yellow stripes along the sides, and a very conspicuous white subdorsal line with a red border above. As there are no eye-spots, this species may be referred to the present group provisionally, although its general marking is very distinct from that of the _Chærocampa_ group. R.M.]

[78] [Eng. ed. Dr. Staudinger has since obtained the caterpillar of _C. Alecto_ from Beyrout; it possesses “a very distinct subdorsal line, and on the fourth segment a beautiful eye-spot, which is repeated with gradual diminution to segments 7-8”.]

[79] Figured in “A Catalogue of Lepidopterous Insects in the Museum of the East India Company,” by Thomas Horsfield and Frederick Moore. London, 1857. Vol. i., Pl. XI.

[80] Figured in Trans. Ent. Soc., New Series, vol. iv., Pl. XIII.

[81] _Ibid._

[82] [The following species figured by Butler (_loc. cit._ Pls. XC. and XCI.) appear to belong to the second group--_Chærocampa Japonica_, Boisd., which is figured in two forms, one brown, and the other green. The former has two distinct ocelli on the fourth and fifth segments, and a distinct rudiment on the sixth, whilst the subdorsal line extends from the second eye-spot to the caudal horn, and beneath this line the oblique lateral stripes stand out conspicuously in dark brown on a lighter ground. The ocelli are equally well developed on the fourth and fifth segments in the green variety, the subdorsal line commencing on the sixth segment, and extending to the caudal horn; there is no trace of a third eye-spot, nor are there any oblique lateral stripes; the insect is almost the exact counterpart of _C. Elpenor_ in its fourth stage. (See Fig. 21, Pl. IV.) _Pergesa Mongoliana_, Butl., is brown, without a trace of the subdorsal line except on the three front segments, and with only one large eye-spot on the fourth segment. _Chærocampa Lewisii_, Butl., from Japan, is likewise figured in two forms. The brown variety has the subdorsal line on the three front segments only, distinct ocelli on the fourth and fifth segments, and gradually diminishing rudiments on the remaining segments. The green form appears to be transitional between the present and the third group, as it possesses a distinct, but rudimentary eye-spot on the third segment, besides the fully developed ones on the fourth and fifth, and very conspicuous, but gradually decreasing repetitions of rudimentary ocelli on segments 6-10. To this group may be added _Chærocampa Aristor_, Boisd., the caterpillar of which is figured by Burmeister (Lép. Rép. Arg., Pl. XV., Fig. 4) in the characteristic attitude of alarm, with the front segments retracted, and the ocelli on the fourth segment prominently exposed. The subdorsal line is present in this species. Burmeister also figures two of the early stages (Pl. XV., Fig. 7, A and B), and describes the complete development of _Philampelus Labruscæ_, another species belonging to the subfamily _Chærocampinæ_. The earliest stage (3-4 days old) is simple green, with no trace of any marking except a black spot on each side of the fourth segment, the position of the future ocelli. A curved horn is present both in this stage and the following one, during which the caterpillar is still green, but now has seven oblique red lateral stripes. The caudal horn is shed at the second moult, after which the colour becomes darker, the adult larva (figured by Madame Mérian, in her work on Surinam, pl. 34 and Sepp., pl. 32) being mottled brown. In addition to the ocellus on the fourth segment, there is another slightly larger on the eleventh segment, so that this species may perhaps be another transition to the third group; but our knowledge is still too imperfect to attempt to generalize with safety. R.M.]

[83] Cat. Lep. Ins. East Ind. Comp., Pl. XIII. [Figured also by Butler (=_Chæerocampa Silhetensis_, Walker), _loc. cit._ Pl. XCII., Fig. 8. R.M.]

[84] Cat. Lep. Ins. East Ind. Comp., Pl. XIII. [Figured also by Butler, _loc. cit._ Pl. XCI., Fig. 1. R.M.]

[85] Horsfield and Moore, _loc. cit._ Pl. X.

[86] _Ibid._ [=_Pergesa Acteus_, Walker. R.M.]

[87] [Figured also by Burmeister, _loc. cit._ Pl. XV., Fig. 3. R.M.]

[88] Horsfield and Moore, _loc. cit._, Pl. XI.

[89] To be accurate this should be designated the infra-spiracular line; but this term cannot be well applied except in cases where there is also a supra-spiracular line, as, for instance, in _Anceryx (Hyloicus) Pinastri_.

[90] Upon this fact obviously depends the statement of that extremely accurate observer Rösel, that the caterpillar of _Euphorbiæ_ is but very slightly variable (“Insektenbelustigungen,” Bd. iii. p. 36). I formerly held the same opinion, till I convinced myself that this species is very constant in some localities, but very variable in others. It appears that local influences make the caterpillar variable.

[91] The green is considerably too light in Fig. 45.

[92] “Die Pflanzen und Raupen Deutschlands.” Berlin, 1860, p. 83.

[93] Fig. 62, Pl. VII., is copied from Boisduval.

[94] The fading of the red anteriorly has not been represented in the figure.

[95] [The caterpillar of _Deilephila Euphorbiarum_, figured by Burmeister (Lép. Rép. Arg., Pl. XVI, Fig. 1) belongs to this stage. R.M.]

[96] [In concluding this account of the _Chærocampinæ_ I may call attention to the following species, which have since been figured by Burmeister:--_Pachylia Ficus_, Linn. (_loc. cit._ Pl. XIV., Figs. 1 and 2); during the three first stages the larva is uniformly green, with a yellow subdorsal line, and below this ten oblique yellow stripes slanting away from the head; after the third moult the colour completely changes, the whole area of the body being divided into two distinct portions by the subdorsal line, above which the colour is red, and underneath of a pale green; the oblique stripes have almost disappeared; no occelli nor annuli are present. _Pachylia Syces_, Hübn. (_loc. cit._ Fig. 3); very similar to the last species in its young stages (figured also by Mérian, Surin. pl. 33). _Philampelus Vitis_, Linn. (_loc. cit._ Figs. 4 and 5); two stages represented; between first and second moults green, with oblique paler stripes slanting in same direction as in _Pachylia_, and each one containing a red streak surrounding the spiracle. When adult, the ground-colour is yellow above and green beneath, the whole surface being mottled with deep black and red transverse markings; the oblique stripes whitish, bordered with black at their lower extremities (figured also by Mérian, pls. 9 and 39). _Philampelus Anchemolus_, Cram. (_loc. cit._ Pl. XV., Fig. 1; Mérian, pl. 47); green when young, with seven oblique red stripes; when adult, uniformly brown, with seven pale yellow lateral markings, the first four of which are spots, and the remainder broad oblique stripes slanting forwards. _Philampelus Labruscæ_, (see note 82, p. 195). R.M.]

[97] [_Mimas Tiliæ_ of Butler’s revision. The author states that this genus is “easily distinguished from _Laothoë_ by the form of the wings, the outer margin of secondaries deeply excavated below the apex, and the secondaries narrow and not denticulated.” Here again we have a clashing of the results arrived at by a study of the ontogeny of the larvæ, on the one hand, and the founding of genera on the characters of the imagines only, on the other. Of the three species discussed by Dr. Weismann, Mr. Butler, following other authors, refers _Tiliæ_ to the genus _Mimas_, _Populi_ to _Laothoë_, and _Ocellatus_ to _Smerinthus_. It is to be hoped that when our knowledge of the developmental history of larvæ is more complete in all groups, a reconciliation between the results of the biological investigator and the pure systematist will be brought about, so that a genus may not, as at present, have such very different values when regarded from these two points of view. R.M.]

[98] The caterpillar is thus figured by Rösel.

[99] [In 1879 Mr. E. Boscher found about thirty full-grown caterpillars of this species in the neighbourhood of Twickenham, ten to twelve of which were feeding on _Salix viminalis_, and the remainder, from a locality not far distant, on _Salix triandra_. The whole of the specimens taken on the plant first named, had the red-brown spots above and below the oblique stripes more or less completely developed, as I myself had an opportunity of observing. In these spotted specimens the ground-colour was bright yellowish-green, and in the others this colour was dull whitish-green above, passing into bluish-green below. Should these observations receive wider confirmation, it would be fair to conclude that this species is now in two states of phyletic development, the more advanced stage being represented by the brighter spotted variety. (See also Proc. Ent. Soc. 1879, p. xliv.). Mr. Peter Cameron has recently suggested (Trans. Ent. Soc. 1880, p. 69) that the reddish-brown spots on the _Smerinthus_ caterpillars may serve for purposes of disguise, as they closely resemble, both in colour and form, certain galls (_Phytoptus_) of the food-plants of these species. If this view be admitted, these spots must be considered as a new character, now being developed by natural selection. The variation in the ground-colour of the two forms of _S. Ocellatus_ may possibly be phytophagic, but this can only be decisively settled by a series of carefully conducted experiments. R.M.]

[100] “Insekten-Belustigungen,” Suppl. Pl. 38, Fig. 40.

[101] “Catalogue of Lepidop.” British Museum. [Butler divides the subfamily _Smerinthinæ_ into 17 genera, containing 79 species, viz. _Metamimas_, 2; _Mimas_, 4; _Polyptychus_, 7; _Lophostethus_, 1; _Sphingonæpiopsis_, 1; _Langia_, 2; _Triptogon_, 23; _Laothoë_, 2; _Cressonia_, 3; _Paonias_, 2; _Calasymbolus_, 5; _Smerinthus_, 5; _Pseudosmerinthus_, 2; _Daphnusa_, 4; _Leucophlebia_, 5; _Basiana_, 10; _Cæquosa_, 1. R.M.]

[102] “Cabinet Orient. Entom.,” p. 13, Pl. VI., Fig. 2. [Butler places this species doubtfully among the _Sphinginæ_. R.M.]

[103] “Catalogue of the Lepidop. Insects of the E.I. Co.,” by Horsfield and Moore. Pl. VIII., Fig. 6.

[104] [The larvæ of four other species of this subfamily have since been made known through Mr. Butler’s figures. _Smerinthus Tatarinovii_, Ménetriés (_loc. cit._ Pl. XC., Fig. 16), from Japan, is “pale sea-green, tuberculated with white, with seven lateral, oblique, crimson-edged white stripes.” There is no trace of the subdorsal line shown in the figure, so that this species thus appears to be in the third phyletic stage of development. _Smerinthus Planus_, Walker, from China (_loc. cit._ Pl XCII., Fig. 11), is “pale green, with white or yellow lateral stripes.” A trace of the subdorsal line remains on the front segments, thus showing that the species is in the second phyletic stage of development. _Triptogon Roseipennis_, Butler, from Hakodadi (_loc. cit._ Pl. XCI., Fig. 6), is represented as yellow, with seven oblique white stripes, with large irregular triangular red spots extending from the anterior edge of the stripes, nearly across each segment. It is probably in the third phyletic stage. The Indian _Polyptychus Dentatus_, Cramer (_loc. cit._ Pl. XCI., Fig. 10), is “bluish-green at the sides, with oblique purple stripes, with a broad, dorsal, longitudinal, golden-green band, bordered by subtriangular purple spots, one above each stripe.” The dorsal band is bordered by coloured stripes, which may be the subdorsal lines; but the position in which it is figured, and its very different mode of coloration, make it very difficult to compare satisfactorily with the foregoing species. The genus _Ambulyx_ is closely allied to the _Smerinthinæ_, and the two following species may be here mentioned: _A. Gannascus_, Stoll, figured by Burmeister (_loc. cit._ Pl. XIII., Fig. 5), is green, with a yellow subdorsal line, and seven oblique white lateral stripes, edged with red. _A. Liturata_, Butl. (_loc. cit._ Pl. XCI., Fig. 2), is yellowish-green above, passing into bluish-green below. The subdorsal is present on the three front segments, and is followed by a row of white, elongated patches, one on each segment, these being the upper portions of a row of lateral oblique stripes. The thickened upper extremities of the latter are edged with red, and their arrangement is very suggestive of their having arisen from the breaking up of a subdorsal line. R.M.]

[105] [Butler catalogues 43 species of this genus. R.M.]

[106] The deposition of eggs was accomplished by the insect laying hold of the point of a twig with its legs during flight, and curving its abdomen upwards against a leaf, the wings being kept vibrating. The egg is instantaneously fastened to the leaf. This operation is repeated from twice to four times successively, the moth then hovering over and sucking at the flowers for some time. The eggs exactly resemble in colour the young green buds of _Galium_.

[107] [Figures of a remarkable case of gynandromorphism in a butterfly (_Cirrochroa Aoris_, Doubl.) have recently been published by Prof. Westwood (Trans. Ent. Soc. 1880, p. 113). On the right fore- and hind-wings of a male specimen there are patches of female colouring, thus bearing out in a very striking manner the above views concerning the non-fusibility of characters (in this case sexual) which have been long fixed. Complete (_i.e._ half-and-half) gynandromorphism is not uncommon in butterflies. R.M.]

[108] [I have long held the opinion that the di- and trimorphism displayed by certain butterflies has originated through polymorphism from ordinary variability. I will not here enter into details, but will only cite a few instances indicating the general direction of the arguments. The phenomenon to which I refer is that so ably treated of by Mr. A. R. Wallace (see Part I., p. 32, note 20) and others. One male has often two or more distinctly coloured females, and in such cases one form of the female generally resembles the male in colour. Cases of polymorphic _mimetic_ females may for the present be excluded, in order to reduce the argument to its greatest simplicity. Thus, in the case of native species, _Colias Edusa_ has two females, one having the orange ground-colour of the male, and the other the well-known light form, var. _Helice_. So, also, _Argynnis Paphia_ has a normal female and the dark melanic form var. _Valezina_. Numerous other cases might be mentioned among exotic species; and, looking at the phenomenon as a whole, it is seen to be one of _gradation_. For instance, our common “Blues” (_Plebeius Icarus_, _P. Thetis_, &c.) have females showing a complete gradation between the ordinary blue male and the brown female coloration. In a large number of specimens of _Callosune Eupompe_ in my cabinet, collected in Arabia by the late J. K. Lord, there is a completely graduated series of females, varying from individuals having the scarlet tips of the fore-wings as strongly developed as in the males, to specimens without a trace of such colouring; and the same is the case with other species of this and allied genera. In such instances it is only necessary for the intermediate female forms to become extinct, in order to have true cases of dimorphism. It is significant that in 1877, when _Colias Edusa_ appeared in this country in such extraordinary profusion, large numbers of _intermediate forms_ were captured, these forming an uninterrupted series connecting the normal female and the var. _Helice_. R.M.]

[109] [Many of our best describers of caterpillars, such as the late Edward Newman, Messrs. Hellins and Buckler, &c., have described the various forms of numerous polymorphic species, but not from the point of view of the comparative morphology and ontogeny of the markings. R.M.]

[110] [In Butler’s revision both these species are placed in the genus _Hemaris_. R.M.]

[111] [This species is figured also by Butler (_loc. cit._ Pl. XC., Fig. 9), who represents it with seven oblique green lines between the spiracles and below the subdorsal line. R.M.]

[112] “Cat. E. Ind. Co. Mus.,” Pl. VIII., Fig. 2. [Walker, Lepidop. Heter. VIII., p. 92, No. 14, 1856; this species is strictly confined to Java. R.M.]

[113] [Eng. ed. The caterpillar is described and figured by Millière, “Iconographie des Chenilles et Lépidoptères inédits,” tome iii., Paris, 1869; also in the Annales, Soc. Linn. de Lyon, 1871 and 1873.] [This sp. = _Hemaris Croatica_, Esper., of Butler’s revision. R.M.]

[114] [The following additional species of the subfamily _Macroglossinæ_ have been figured by Butler:--_Lophura Hyas_, Walk. (_loc. cit._ Pl. XC., Figs. 1 and 2), Hong-Kong, Silhet, and Java. The larva is apparently figured in two stages, the younger being red-brown with oblique white stripes, and the head and three front segments green. The larger specimen is green, mottled with red-brown, and no oblique stripes. In both figures the subdorsal line is indicated. The whole colouring is very suggestive of protective resemblance. _Hemaris Hylas_, Linn., from China, Japan, Ceylon, India, Australia, and Africa (_loc. cit._ Pl. XC., Fig. 4). The upper part of the body is light blue, and the lower part green, the two areas being separated by a white subdorsal line bordered above with brown. The dorsal line is feebly represented. _Macroglossa Belis_, Cram., N. India (_loc. cit._ Pl. XC., Fig. 6), is figured with the ground-colour deep indigo; a conspicuous white subdorsal, and a yellow spiracular line is present; on the side of each segment, between the two lines mentioned, there is a large red spot with a yellow nucleus (? eye-spots), the spots decreasing in size towards the head and tail; these probably confer upon this species some special protective advantage. _Macroglossa Pyrrhosticta_, Butler, China and Japan (_loc. cit._ Pl. XC., Fig. 8), is greenish-white with dorsal and subdorsal lines, and seven dark oblique stripes along the sides, below the subdorsal line. Of the foregoing species _Hemaris Hyas_ appears to be in the same phyletic stage as _M. Stellatarum_ and _M. Croatica_, &c., whilst _M. Pyrrhosticta_ is probably, together with _M. Corythus_ and _M. Gilia_, in another and more advanced stage, which is also passed through by _Lophura Hyas_ in the course of its ontogenetic development. This last species (adult) and _M. Belis_ may represent phyletic stages still further advanced. _Caliomma Pluto_, Walk., of which the caterpillar is figured by Burmeister (_loc. cit._ Pl. XIII., Fig. 1), appears to be a case of special protective resemblance to a twig or branch of its food-plant. Figured also by Chavannes; Bull. Soc. Vadoise des Sci. Nat., Dec. 6th 1854. R.M.]

[115] [Genus _Pterogon_, Boisd., = _Proserpinus_ and _Lophura_ (part). Butler, _loc. cit._ p. 632. The species above treated of = _Proserpinus Œnotheræ_, Fabr. R.M.]

[116] [These species = _Thyreus Abboti_ and _Proserpinus Gauræ_ of Butler’s revision. Of the former he states:--“Transformations described, and larva and imago figured, Am. Ent. ii. p. 123, 1870; the larva is also figured by Scudder in Harris’s ‘Correspondence,’ Pl. III., Fig. 1 (1869), and by Packard in his ‘Guide,’ p. 276, Fig. 203.” R.M.]

[117] [_Proserpinus (Sphinx) Gorgon_, Esp. R.M.]

[118] Rösel, _loc. cit._ vol. iii., p. 26, note.

[119] Figured and described by Abbot and Smith. [_Macrosila (Sphinx) Cingulata_ is figured also by Burmeister, _loc. cit._ Pl. XII., Fig. 1. R.M.]

[120] Figured in “Cat. Lep. E. Ind. Co.”

[121] See the figure in Sepp’s Surinam Lepidoptera, P. 3, Pl. CI., 1848. A specimen in alcohol of the adult caterpillar is in the Berlin Museum. [The following is the synonymy of the above mentioned species:--_Macrosila Hasdrubal_, Walk. = _Pseudosphinx (Sphinx) Tetrio_, Linn.; _M. Cingulata_ = _Protoparce (Sphinx) Cingulata_, Fabr.; _M. Rustica_ = _Protoparce (Sphinx) Rustica_, Fabr.; _Sphinx Convolvuli_, Linn. = _Protoparce Convolvuli_; _S. Carolina_, Linn. = _P. Carolina_; the other species remain in the genera, as given above. The following additional species of _Sphinginæ_ and _Acherontiinæ_ have been figured by Butler:--_Pseudosphinx Cyrtolophia_, Butl., from Madras (_loc. cit._ Pl. XCI., Figs. 11 and 13); _Protoparce Orientalis_, Butl., from India, China, Java, &c. (Pl. XCI., Fig. 16); _Diludia Vates_, Butl. from India, &c. (Pl. XCI., Fig. 18); _Nephele Hespera_, Fabr., from India, Australia, &c. (Pl. XCI., Fig. 20); _Acherontia Morta_, Hübn., from Java, China, India, &c. (Pl. XCII., Fig. 9); and _A. Medusa_, Butl., from nearly the same localities as the last (Pl. XCII., Fig. 10). Most of these species fall under Dr. Weismann’s general remarks, so that it is unnecessary to give detailed descriptions. The most divergent marking is that of _P. Cyrtolophia_, which has a broad white dorsal line bordered with pink, and two large pink ovals on the back of the four anterior segments, the hindmost and larger of these being bisected by the dorsal line. In _N. Hespera_ the subdorsal line is present on segments 6 to 11 only, and it is highly significant that the oblique stripes are absent from these segments, but are present on the anterior segments, where the subdorsal line fails. With reference to the larva of _A. Atropos_, Mr. Mansel Weale states (Proc. Ent. Soc. 1878, p. v.) that in S. Africa the ordinary form feeds generally on _Solanaceæ_, whilst the darker and rarer variety is found only on species of _Lantana_. The following species of these subfamilies are figured by Burmeister: _Amphonyx Jatrophæ_ (_loc. cit._ Pl. XI., Fig. 1); _Protoparce (Diludia) Florestan_, Cram. (Fig. 2); _Sphinx Justiciæ_, Walk. (Fig. 3); _Protoparce (Diludia) Lichenea_, Walk. (Fig. 4); _Sphinx (Protoparce) Cingulata_, Fabr. (Pl. XII., Fig. 1); and _Sphinx Cestri_ (Fig. 5). All these species have the characteristic Sphinx-like markings. _Dilophonota Ello_, Linn. (Pl. XII., Fig. 2), is greenish-brown with a yellow subdorsal line, and _D. Hippothöon_ (Fig. 4), yellow with a whitish subdorsal. Neither of these has oblique stripes. _D. Œnotrus_, Cram. (Fig. 3), has neither stripes nor subdorsal, but is uniform brown above, passing into green beneath. _Protoparce Albiplaga_, Walk. (Pl. XIII., Fig. 2, also Mérian, Pl. III., and Abbot and Smith, I., Pl. XXIV.), pale green with large yellow, black-bordered patches surrounding the spiracles. _Pseudosphinx Tetrio_, Linn. (Pl. XIII., Fig. 3), and _P. Scyron_ (Fig. 4) are black with broad transverse belts, yellow and white respectively, encircling the middle of each segment. These light bands serve very effectively to break up the uniform surface of the large bodies of these insects, but the whole marking is suggestive of distastefulness. R.M.]

[122] [The species referred to is placed by Butler in Hübner’s genus _Hyloicus_. R.M.]

[123] [= _Ellema Coniferarum_, of Butler’s revision. R.M.]

[124] [= _Dilophonota Ello_ of Butler’s revision. R.M.]

[125] “Synopsis of the North American Sphingides.” Philadelphia, 1859.

[126] [The larvæ of many moths which feed on deciduous trees during the autumn and hibernate, are stated to feed on low-growing plants in the spring, before the buds of their food-trees open. On the other hand, low-plant feeders, such as _Triphæna Fimbria_, &c., are stated to sometimes feed at night in early spring on the buds of trees. The habits and ontogeny of these species are of special interest in connection with the present researches, and are well worthy of investigation. R.M.]

[127] “Neuer Beitrag zum geologischen Beweise der Darwin’schen Theorie.” 1873, Nos. 1 and 2. [This principle, in common with many others which have only been completely worked out of late years, is foreshadowed by Darwin. Thus, he states when speaking of inheritance at corresponding periods of life: “I could give a good many cases of variations (taking the word in the largest sense) which have supervened at an earlier age in the child than in the parent” (“Origin of Species,” 1st ed., 1860, p. 444). In the case of inherited diseases also: “It is impossible to ... doubt that there is a strong tendency to inheritance in disease at corresponding periods of life. When the rule fails, the disease is apt to come on earlier in the child than in the parent; the exceptions in the other direction being very much rarer.” (“Variation of Animals and Plants under Domestication,” 1st ed., 1868, vol. ii., p. 83.) R.M.]

[128] [If the reddish-brown spots on the larva of _S. Populi_ have the protective function assigned to them by Mr. Peter Cameron (Trans. Ent. Soc. 1880, p. 69), it can be readily understood that they would be of service to the insect in the fourth stage, and the backward transference of this character might thus be accelerated by natural selection, in accordance with the above principles. (See, also, note 100, p. 241.) R.M.]