Studies in the Theory of Descent, Volume I

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.]

129

[For cases of correlation of habit with protective resemblance in larvæ, see a paper in “Ann. and Mag. of Nat. Hist.,” Feb., 1878, pp. 159, 160. Also Fritz Müller on a Brazilian Cochliopod larva, Trans. Ent. Soc. 1878, p. 223. Mr. Mansel Weale states, with reference to S. African Sphingidæ (Proc. Ent. Soc. 1878, p. vi.), that many species when seized “have a habit of doubling up the body, and then jumping a considerable distance with a spring-like action. This is especially the case with species having eye-like markings; and it is probable that if attacked by birds in a hesitating manner, such species might effect their escape amid the grass or foliage.” Many of the defensive weapons and habits of larvæ are doubtless means of protection from ichneumons and other parasitic foes. In the case of saw-flies, Mr. Peter Cameron has shown (Trans. Ent. Soc. 1878, p. 196) that the lashing about of the posterior part of the body may actually frighten away such enemies. The grotesque attitude and spider-like appearance and movements of the caterpillar of Stauropus Fagi are considered by Hermann Müller (“Kosmos,” Nov., 1879, p. 123) to be means of protection from ichneumons. Among the most remarkable means of defence possessed by larvæ is that of secreting a liquid, which Mr. W. H. Edwards has shown, in the case of certain North American Lycænidæ (“Canadian Entomologist.” vol. x., 1878, pp. 3–9 and 131–136), to be attractive to ants, who regularly attend these caterpillars, in the same manner and for the same purpose as they do our aphides. The mutual advantage derived by the ants and larvæ was discovered in the case of Lycæna Pseudargiolus. Mr. Edwards states that the mature larva of this species is singularly free from Hymenopterous and Dipterous parasites: – “Why this species, and doubtless many other Lycænæ, are thus favoured will, perhaps, in some degree appear from a little incident to be related. On 20th June, in the woods, I saw a mature larva on its food-plant; and on its back, facing towards the tail of the larva, stood motionless one of the larger ants… At less than two inches behind the larva, on the stem, was a large ichneumon-fly, watching its chance to thrust its ovipositor into the larva. I bent down the stem, and held it horizontally before me, without alarming either of the parties. The fly crawled a little nearer and rested, and again nearer, the ant making no sign. At length, after several advances, the fly turned its abdomen under and forward, thrust out its ovipositor, and strained itself to the utmost to reach its prey. The sting was just about to touch the extreme end of the larva, when the ant made a dash at the fly, which flew away, and so long as I watched – at least five minutes – did not return. The larva had been quiet all this time, its tubes out of sight, and head buried in a flower-bud, but the moment the ant rushed and the fly fled, it seemed to become aware of the danger, and thrashed about the end of its body repeatedly in great alarm. But the tubes were not protruded, as I was clearly able to see with my lens. The ant saved the larva, and it is probable that ichneumons would in no case get an opportunity to sting so long as such vigilant guards were about. It strikes me that the larvæ know their protectors, and are able and willing to reward them. The advantage is mutual, and the association is friendly always.” Those who are familiar with Mr. Belt’s description of the standing armies of ants kept by the “bull’s-horn thorn” (“Naturalist in Nicaragua,” pp. 218–222) and by certain Cecropiæ and Melastomæ, will be struck with the analogy between these and the foregoing case. R.M.]

130

[The adaptive resemblance is considerably enhanced in Catocala and in Lasiocampa Quercifolia by the row of fleshy protuberances along the sides of these caterpillars, which enables them to rest on the tree trunks by day without casting a sharp shadow. The hairs along the sides of the caterpillar of Pæcilocampa Populi doubtless serve the same purpose. (See a paper by Sir John Lubbock, Trans. Ent. Soc. 1878, p. 242; also Peter Cameron, ibid., 1880, p. 75.) It is well known to collectors that one of the best methods of finding the caterpillars of the Catocalæ is to feel for them by day on the barks of their respective food-trees, or to beat for them at night. R.M.]

131

[See Wallace’s “Contributions to the Theory of Natural Selection,” 1st ed., p. 62. Also a paper in “Ann. Mag. Nat. Hist.” Feb. 1878, p. 159, for cases in point. Rösel in 1746 mentioned this habit in Calocampa Exoleta. Hermann Müller has recorded many other similar instances on the authority of Dr. Speyer; see “Kosmos,” Nov., 1879, p. 114. R.M.]

132

[Andrew Murray called attention to this fact in 1859 (“Edinburgh New Philos. Journ.,” Jan., 1860, p. 9). This view is also corroborated by the fact that no internal feeders are green; see note 142, p. 310 and Proc. Zoo. Soc. 1873, p. 159. R.M.]

133

[Proc. Ent. Soc. March 4th, 1867; and “Contributions to the Theory of Natural Selection,” 1st ed., pp. 117–122; also Darwin’s “Descent of Man,” 2nd ed., p. 325. Among the most important recent additions to the subject of the colours, spines, and odours of caterpillars, I may call attention to a paper by Fritz Müller (“Kosmos,” Dec., 1877), the following abstract of which I communicated to the Entomological Society (Proc. 1878, pp. vi, vii): – “The larvæ of Dione Juno and Acræa Thalia live gregariously, and are brown in colour; they are covered with spines, but, being of dull colours, their spiny protection (which in the case of D. Juno is very imperfect) would not preserve them unless they were distinguished as inedible at the right time, and not after being seized, in accordance with the principles laid down by Mr. Wallace. It is suggested that the social habits of the larvæ which lead then to congregate in large numbers, make up for their want of colour, since their offensive odour then gives timely warning to an approaching enemy. The caterpillars of Colænis Julia and Dione Vanillæ are equally wanting in bright colours, but are solitary in their habits, and these species rest on the under side of the leaf when feeding. On the other hand, the caterpillars of Heliconius Eucrate, Colænis Dido, and C. Isabella, which are of solitary habits, and which freely expose themselves, are very gaudily coloured, and therefore most conspicuous. As examples of nearly allied larvæ, of which some species are gregarious and others solitary, Fritz Müller mentions Morpho and Brassolis, which are gregarious; while Opsiphanes and Caligo are solitary. The larva of Papilio Pompeius also is gregarious, and those of P. Nephalion, P. Polydamas, and P. Thoas are solitary… Fritz Müller sums up his observations by remarking that those caterpillars which live alone, and lack the bright colouring as a sign of offensiveness, must hide themselves; as those of C. Julia and D. Vanillæ. The spiny covering is much less a protection against birds than against smaller enemies; and they may, by the protective habit of living together, diffuse around themselves an offensive atmosphere, even to man, and thus gradually becoming shorter (as with D. Juno), the spines of these caterpillars become useless, and finally are altogether dropped.” See also Sir John Lubbock’s “Note on the Colours of British Caterpillars,” Trans. Ent. Soc. 1878, p. 239. Mr. Peter Cameron finds (Trans. Ent. Soc. 1880, pp. 71 and 75) that these remarks are also applicable to the larvæ of certain saw-flies. In 1877 Mr. J. W. Slater published a paper “On the Food of gaily-coloured Caterpillars” (Trans. Ent. Soc. 1877, p. 205), in which he suggested that such caterpillars might derive their distasteful qualities from feeding on plants containing poisonous or otherwise noxious principles. A much larger number of observations will be required, however, before this view can be accepted as of general application. A beautiful illustration of the theory of warning colours is given by Belt in his “Naturalist in Nicaragua,” p. 321. All the frogs found in the woods round St. Domingo are, with one exception, protectively coloured; they are of nocturnal habits, and are devoured by snakes and birds. The exception was a species of bright red and blue colours, which hopped about by day and made no attempt at concealment. From these facts Mr. Belt concluded that this species was inedible, and on trying the experiment with ducks and fowls this was found to be the case. R.M.]