Studies in the Theory of Descent, Volume I

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 (#Page_19)–22 (#Page_22), and 53 (#Page_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.