SILK-PRODUCING BOMBYCES AND OTHER LEPIDOPTERA REARED IN 1881.
By ALFRED WAILLY, Membre Lauréat de la Société d'Acclimatation de France.
By referring to my reports for the years 1879 and 1880, which appeared in the Journal of the Society of Arts, February 13 and March 5, 1880, February 25 and March 4, 1881, it will be seen that the bad weather prevented the successful rearing in the open air of most species of silk-producing larvæ. In 1881, the weather was extremely favorable up to the end of July, but the incessant and heavy rains of the month of August and beginning of September, proved fatal to most of the larvæ when they were in their last stages. However, in spite of my many difficulties, I had the satisfaction of seeing them to their last stage. Larvæ of all the silk-producing bombyces were preserved in their different stages, and can be seen in the Bethnal-green Museum. In July, when the weather was magnificent, the little trees in my garden were literally covered with larvæ of more species than I ever had before, and two or three more weeks of fair weather would have given me a good crop of cocoons, instead of which I only obtained a very small number. The sparrows, as usual, also destroyed a quantity of worms, in spite of wire or fish-netting placed over some of the trees.
On the trees were to be seen--Attacus cynthia (the Ailantus silkworm), the rearing of which was, as usual, most successful; Samia cecropia and Samia gloveri, from America; also hybrids of Gloveri cecropia and Cecropia gloveri; Samia promethea and Telea polyphemus; Attacus pernyi, and a new hybrid, which I obtained this last season by the crossing of Pernyi with Royle. For the first time I reared Actias selene, from India, on a nut-tree in the garden, and Attacus atlas, on the ailantus. The Selene larvæ reached their fifth and last stage. The Atlas larvæ only reached the third stage, and were destroyed by the heavy rains; only two remained on the tree till about the 8th or 9th of September, when they had to be removed. I shall now reproduce the notes I took on some of the various species I reared.
Actias Selene.--With sixty cocoons I only obtained one pairing. The moths emerged from the beginning of March till the 13th of August, at intervals of some duration, or in batches of males or females. I obtained a pairing of Selene on the 30toh of June, 1881, and the worms commenced to hatch on the 13th of July. The larvæ in first stage are of a fine brown-red, with a broad black band in the middle of the body. The second stage commenced on the 20th of July; larvæ, of a lighter reddish color, without the black band; tubercles black. Third stage commenced on the 28th of July; larvæ green; the first four tubercles yellow, with a black ring at the base; other tubercles, orange yellow. Fourth stage commenced on the 6th of August; larvæ green; first four tubercles golden-yellow, the others orange-red. Fifth stage commenced on the 19th of August; first four tubercles yellow, with a black ring at the base; other tubercles yellow, slightly tinged with orange-red; lateral band brown and greenish yellow; head and forelegs dark-brown. As stated before, the larvæ were reared on a nut-tree in the garden, till the last stage. Selene feeds on various trees--walnut, wild cherry, wild pear, etc. In Ceylon (at Kandy), it is found on the wild olive tree. As far as I am informed by correspondents in Ceylon, this species is not found--or is seldom found--on the coasts, but Attacus atlas and Mylitta are commonly found there.
Attacus (antheroea) roylei (with sixty cocoons); three pairings only were obtained, and this species I found the most difficult to pair in captivity. Two moths emerged on the 5th of March, a male and a female, and a pairing was obtained; but the weather being then too cold, the ova were not fertile, the female moth, after laying about two hundred eggs, lived till the 22d of March, which is a very long time; this was owing to the low temperature. The moths emerged afterward from the 8th of April till the 25th of June. A pairing took place on the 2d of June, and another on the 6th of June.
Roylei (the Himalaya oak silkworm) is very closely allied to Pernyi, the Chinese oak silkworm; the Roylei moths are of a lighter color, but the larvæ of both species can hardly be distinguished from one another. The principal difference between the two species is in the cocoon. The Roylei cocoon is within a very large and tough envelope, while that of Pernyi has no outer envelope at all. The larvæ of Roylei I reared did not thrive, and the small number I had only went to the fourth stage, owing to several causes. I bred them under glass, in a green-house. A certain number of the larvæ were unable to cut the shell of the egg.
Here are a few notes I find in my book: Ova of Roylei commenced to hatch on the 29th of June; second stage commenced on the 9th of July. The larvæ in the first two stages seemed to me similar to those of Pernyi, as far as I could see. In second stage, the tubercles were of a brilliant orange-red; on anal segment, blue dot on each side. Third stage, four rows of orange-yellow tubercles, two blue dots on anal segment, brilliant gold metallic spots at the base of the tubercles on the back, and silver metallic spots at the base of the tubercles on the sides. No further notes taken.
One of my correspondents in Vienna (Austria) obtained a remarkable success in the rearing of Roylei. From the twenty-five eggs he had twenty-three larvæ hatched, which produced twenty-three fine cocoons. The same correspondent, with thirty-five eggs of Samia gloveri, obtained twenty cocoons. My other correspondents did not obtain any success in rearing these two species, as far as I know.
Hybrid Roylei-Pernyi.--I have said that it is extremely difficult to obtain the pairing of Roylei moths in captivity. But the male Pernyi paired readily with the female Roylei. I obtained six such pairings, and a large quantity of fertile ova. The pairings of Roylei (female) with Pernyi (male) took place as follows: two on the 21st of May, one on the 3d of June, two on the 4th of June, and one on the 6th.
The larvæ of this new hybrid, Roylei-Pernyi, contrary to what might have been expected, were much easier to rear than those of Roylei, and the cocoons obtained are far superior to those of Roylei, in size, weight, and richness of silk. The cocoon of my new hybrid has, like Roylei, an envelope, but there is no space between this envelope and the true cocoon inside. Therefore, this time, the crossing of two different species (but, it must be added, two very closely allied species) has produced a hybrid very superior, at least to one of the types, that of Roylei. The cocoons of the hybrid Roylei-Pernyi seem to me larger and heavier than any Pernyi cocoons I have as yet seen.
The larvæ of this new hybrid have been successfully reared in France, in Germany, in Austria, and in the United States of North America. The cocoons obtained by Herr L. Huessman, one of my German correspondents, are remarkable for their size and beauty. The silk is silvery white.
I have seventeen cocoons of this hybrid species, which number may be sufficient for its reproduction. But the question arises, "Will the moths obtained from these cocoons be susceptible of reproduction?"
In my report on Lepidoptera for the year 1879, I stated, with respect to hybrids and degeneracy, that hybrids had been obtained by the crossing of Attacus pernyi and Attacus yama-maï, but that, although the moths (some of which may be seen in the Bethnal-green Museum) are large and apparently perfect in every respect, yet these hybrids could not be reproduced. It must be stated that these two species differ essentially in one particular point. Yama-maï hibernates in the ovum state, while Pernyi hibernates in the pupa state. The hybrids hibernated in the pupa state. Roylei, as Pernyi, hibernates in the pupa state.
In the November number, 1881, of "The Entomologist," Mr. W.F. Kirby, of the British Museum, wrote an article having for its title, "Hermaphrodite-hybrid Sphingidæ," in which, referring to hybrids of Smerinthus ocellatus and populi, he says that hermaphroditism is the usual character of such hybrids.
I extract the following passage from his article: "I was under the impression that hermaphroditism was the usual character of these hybrids; and it has suggested itself to my mind as a possibility, which I have not, at present, sufficient data either to prove or to disprove, that the sterility of hybrids in general (still a somewhat obscure subject) may perhaps be partly due to hybridism having a tendency to produce hermaphroditism."
Now, will the moths of new hybrid Roylei pernyi (which I expect will emerge in May or June, 1882) have the same tendency to hermaphroditism as has been observed with the hybrids obtained by the crossing of Smerinthus populi with Sm. ocellatus? I do not think that such will be the case with the moths of the hybrid Roylei-pernyi, on account of the close relationship of Roylei with Pernyi, but nothing certain can be known till the moths have emerged. Here are the few notes taken on the hybrid Roylei-pernyi: Ova commenced to hatch on the 12th of June; these were from the pairing which had taken place on the 21st of May. Larvæ, black, with long white hairs. Second stage commenced on the 21st of June. Larva, of a beautiful green; tubercles orange-yellow; head dark brown. Third stage commenced on the 1st of July; fourth stage on the 7th. Larva of same color in those stages; tubercles on the back, violet-blue or mauve; tubercles on the sides, blue. Fifth stage commenced on the 18th of July. Larva, with tubercles on back and sides, blue, or violet-blue. First cocoon commenced on the 10th of August. Want of time prevented me from taking fuller and more accurate notes.
Attacus Atlas.--For the first time, as stated before, I attempted the rearing of a small number of Atlas larvæ in the open air on the ailantus tree, but had to remove the last two remaining larvæ in September; the others had all disappeared in consequence of the heavy and incessant rains. These larvæ were from eggs sent to me by one of my German correspondents. The pairing of the moths had taken place on the 17th of July, and the eggs had commenced to hatch on the 4th of August.
I had about eighty cocoons of another and larger race of Atlas imported from the Province of Kumaon, but only eight moths emerged at intervals from the 31st of July to the 30th of September. Not only did the moths emerge too late in the season, but there never was a chance of obtaining a pairing. In my report on Indian silkworms, published in the November number of the "Bulletin de la Societe d'Acclimatation," for the year 1881, compiled from the work of Mr. J. Geoghegan, I reproduce the first appendix of Captain Thomas Hutton to Mr. Geoghegan's work, in which are given the names of all the Indian silkworms known by him up to the year 1871.
Of Attacus atlas, Captain Hutton says: "It is common at 5,500 feet at Mussoorie, and in the Dehra Doon; it is also found in some of the deep warm glens of the outer hills. It is also common at Almorah, where the larva feeds almost exclusively upon the 'Kilmorah' bush or Berberis asiatica; while at Mussoorie it will not touch that plant, but feeds exclusively upon the large milky leaves of Falconeria insignis. The worm is, perhaps, more easily reared than any other of the wild bombycidæ."
I will now quote from letters received from one of my correspondents in Ceylon, a gentleman of great experience and knowledge in sericulture.
In a letter dated 24th August, 1881, my correspondent says: "The Atlas moth seems to be a near relation of the Cynthia, and would probably feed on the Ailantus. Here it feeds on the cinnamon and a great number of other trees of widely different species; but the tree on which I have kept it most successfully in a domestic state is the Milnea roxburghiana, a handsome tree, with dark-green ternate leaves, which keep fresh long after being detached from the tree. I do not think the cocoon can ever be reeled, as the thread usually breaks when it comes to the open end. I have tried to reel a great many Atlas cocoons, but always found the process too tedious and troublesome for practical use.
"The Mylitta (Tusser) is a more hardy species than the Atlas, and I have had no difficulty in domesticating it. Here it feeds on the cashew-nut tree, on the so-called almond of this country (Terminalia catappa), which is a large tree entirely different from the European almond, and on many other trees. Most of the trees whose leaves turn red when about to fall seem to suit it, but it is not confined to these. In the case of the Atlas moth, I discovered one thing which may be well worth knowing, and that was, that with cocoons brought to the seaside after the larvæ had been reared in the Central Provinces, in a temperature ten or twelve degrees colder, the moths emerged in from ten to twenty days after the formation of the cocoon. The duration of the pupa stage in this, and probably in other species, therefore, depends upon the temperature in which the larvæ have lived, as well as the degree of heat in which the cocoons are kept; and in transporting cocoons from India to Europe, I think it will be found that the moths are less liable to be prematurely forced out by the heat of the Red Sea when the larvæ have been reared in a warm climate than when they have been reared in a cold one.
"I do not agree with the opinion expressed in one of your reports, that the short duration of the larva stage, caused by a high temperature, has the effect of diminishing the size of the cocoons, because the Atlas and Tusser cocoons produced at the sea-level here are quite as large as those found in the Central Provinces at elevations of three thousand feet or more. According to the treatise on the "Silk Manufacture," in "Lardner's Cyclopedia," the Chinese are of opinion that one drachm of mulberry silkworms' eggs will produce 25 ounces of silk if the caterpillars attain maturity within twenty-five days; 20 ounces if the commencement of the cocoons be delayed until the twenty-eighth day; and only 10 ounces if it be delayed until between the thirtieth and fortieth day. If this is correct, a short-lived larva stage must, instead of causing small cocoons, produce just the contrary effect."
In another letter, dated November 25, 1881, my correspondent says: "I am sorry that you have not had better success in the rearing of your larvæ, but you should not despair. It is possible that the choice of an improper food-plant may have as much to do with failures as the coldness and dampness of the English climate. I lost many thousands of Atlas caterpillars before I found out the proper tree to keep them on in a domesticated state; and when I did attain partial success, I could not keep them for more than one generation, till I found the Milnea roxburghiana to be their proper food plant. I do not know the proper food-plant of the Mylitta (Tusser), but I have succeeded very well with it, as it is a more hardy species than the Atlas. Though a Bombyx be polyphagous in a state of nature, yet I think most species have a tree proper to themselves, on which they are more at home than on any other plant. I should like, if you could find out from some your correspondents in India, on what species of tree Mylitta cocoons are found in the largest numbers, and what is about the greatest number found on a single tree. The Mylitta is common enough here, but there does not seem to be any kind of tree here on which the cocoons are to be found in greater numbers than twos and threes; and there must be some tree in India on which the cocoons are to be found in much greater plenty, because they could not otherwise be collected in sufficient quantity for manufacturing purposes. The Atlas is here found on twenty or more different kinds of trees, but a hundred or a hundred and fifty cocoons or larvæ may be found on a single tree of Milnea roxburghiana, while they are to be found only singly, or in twos and threes, on any other tree that I know of. The Atlas and Mylitta seem to be respectively the Indian relations of the Cynthia and Pernyi. It is, therefore, probable that the Ailantus would be the most suitable European tree for the Atlas, and the oak for the Mylitta."
Attacus mylitta (Antheræa paphia).--I did not receive a single cocoon of this species for the season 1881. My stock consisted of seven cocoons, from the lot received from Calcutta at the end of February, 1880. Five were female, and two male cocoons; one of the latter died, thus reducing the number to six. The moths emerged as follows: One female on the 21st of June, one female on the 26th, one female on the 28th, one female on the 1st of July, and one male on the 3d of August; the latter emerging thirty-four days too late to be of any use for rearing purposes. The last female moth emerged, I think, about the end of September. These cocoons had hibernated twice, as has been the case with other Indian species. I had Indian cocoons which hibernated even three times.
Attacus cynthia, from the province of Kumaon.--With the Atlas cocoons, a large quantity of Cynthia cocoons were collected in the province of Kumaon. Both species had, no doubt, fed on the same trees; as the Cynthia, like the Atlas cocoons, were all inclosed in leaves of the Berberis vulgaris, which shows that Cynthia is also a polyphagous species. It is already known that it feeds on several species of trees, besides the ailantus, such as the laburnum, lilac, cherry, and, I think, also on the castor-oil plant; the common barberry has, therefore, to be added to the above food plants.
These Kumaon Cynthia cocoons were somewhat smaller and much darker in color than those of the acclimatized Cynthia reared on the ailantus. The moths of this wild Indian Cynthia were also of a richer color than those of the cultivated species in Europe.
During the summer 1881, I saw cocoons of my own Cynthia race obtained from worms which had been reared on the laburnum tree. These cocoons were, as far as I can remember, of a yellowish or saffron color; which I had never seen before. This difference in the color of the cocoon was very likely produced by the change of food, although it has been stated, and I think it may be quite correct, that with many species of native lepidoptera the change of food-plants does not produce any difference of color in the insects obtained. With respect to the Cynthia worms reared on the laburnum instead of the ailantus, it may be that the moths, which will emerge from the yellow cocoons, will be similar to those obtained from cocoons spun by worms bred on the ailantus, and that the only difference will be in the color of the cocoons.
The Kumaon Cynthia cocoons, as I found it to be the case with Indian species introduced for the first time into Europe, did not produce moths at the same time, nor as regularly as the acclimatized species. The moths emerged as follows: One female on the 22d of July; one female on the 25th; one male on the 3d August; one female on the 19th; one male on the 28th of August; one male on the 2d September; one female on the 3d. A pairing was obtained with the latter two. Two males emerged on the 4th of September; one male on the 6th; one male and one female on the 22d; one female on the 23d; and one female on the 25th of September. Five cocoons, which did not produce any moths, contain pupæ, which are still in perfect condition; and the moths will no doubt emerge next summer (1882). As seen in my note, a pairing of this wild Indian Cynthia took place; this was from the evening of the 4th to the 5th of September. The eggs laid by the female moth were deposited in a most curious way, in smaller or larger quantities, but all forming perfect triangles. These eggs I gave to a florist who has been very successful in the rearing of silk-producing and other larvæ; telling him to rear the Cynthia on lilacs grown in pots and placed in a hot-house, which was done. The worms, which hatched in a few days, as they were placed in a hot-house, thrived wonderfully well, and I might say they thrived too well, as they grew so fast and became so voracious that the growth of the lilac trees could not keep pace with the growth of the worms. These, at the fourth stage, became so large that the foliage was entirely devoured, and, of course, the consequence was that all the worms were starved. I only heard of the result of that experiment long after the death of the larvæ; otherwise I should have suggested the use of another plant after the destruction of the foliage of the lilacs; the privet (Ligustrum vulgare) might have been tried, and success obtained with it.
Of such species as Attacus pyri, of Central Europe, and Attacus pernyi, the North Chinese oak silkworm, which I have mentioned in my previous reports, and bred every season for several years, I shall only say that I never could rear Pyri in the open air in London, up to the formation of the cocoon. As to Pernyi, I had, in 1881, an immense quantity of splendid moths, from which I obtained the largest quantity of ova I ever had of this species. I had many thousands of fertile ova of Pernyi, which I was unable to distribute. Many schoolboys reared Pernyi worms, but with what success I do not yet know. The number of fertile ova obtained from Pyri moths was also more considerable than in former years, which was due partly to the good quality of the pupæ, and partly to the very favorable weather in June, at the time the pairings of the moths took place.
Leaving these, I now come to the North American species.
Telea polyphemus.--As I have stated in former years, this is the best North American silkworm, producing a closed cocoon, somewhat smaller than that of Pernyi, but the silk seems as good as that of Pernyi.
The cocoons of Polyphemus I had in 1881 were smaller and inferior in quality to those I had before. Those received in 1878 and 1879 were considerably finer and larger than those which were sent in 1880 and 1881; besides, they were sent in much larger quantities. The cocoons received this year (1882) are finer than those of 1881, but yet they cannot be compared with those of 1878 and 1879.
With about sixty cocoons of Telea polyphemus I only obtained three pairings, which I attribute solely to the weakness of the moths, as the weather was all that could be desired for the pairings. The moths emerged from the 1st of June to the 20th of July. One male moth emerged on the 7th September. This latter was one from a small number of cocoons received from Alabama; the other cocoons of the same race had emerged at the same time as the cocoons from the Northern States. In the Northern States the species is single-brooded; in the Southern States it is double-brooded.
The larvæ of Polyphemus can be bred in the open air in England, almost as easily as those of Pernyi, and even Cynthia; they will pass through their five stages and spin their cocoons on the trees, unless the weather should be unexceptionally cold and wet, as was the case during the month of August, 1881, when the larvæ had reached their full size; they were reared this year on the nut-tree, and some on the oak. The species is extremely polyphagous, and will feed well on oak, birch, chestnut, beech, willow, nut, etc.
The moth of Polyphemus is very beautiful, and, as in some other species, varies in its shades of color. The larva is of a transparent green, of extreme beauty; the head is light brown; without any black dots, as in Pernyi; the spines are pink, and at the base of each of them there is a brilliant metallic spot. When the sun shines on them the larvæ seem to be covered with diamonds. These metallic spots at the base of the spines are also seen on Pernyi, Yama mai, Mylitta, and other species of the genus Antheræa, all having a closed cocoon, but none of these have so many as Polyphemus.
The cocoons of the species of the genus Actias are closed, but the larvæ have not the metallic spots of the species of the genus Antheræa.
Samia Gloveri.--Three North American silk-producing bombyces, very closely allied, have been mentioned in my previous reports; they are; Samia ceanothi, from California; Samia gloveri, from Utah and Arizona; and Samia cecropia, commonly found in most of the Northern States--the latter is the best and largest silk producer. Crossings of these species took places in 1880, and, as I stated before, the ova obtained from a long pairing between a Ceanothi female with a Gloveri male, were the only ones which were fertile. The Gloveri cocoons received in 1880 were of a very inferior quality, and produced moths from which no pairings could be obtained, although some crossings took place. In 1881, the Gloveri cocoons, on the contrary, produced fine, healthy moths; yet only five pairings could be obtained, with about one hundred cocoons. Besides these five pairings, a quantity of fertile ova were obtained by the crossings of S. gloveri (female) with S. cecropia (male), and Cecropia (female) with Gloveri (male). No success, so far as I know, was obtained with the rearing of the hybrid larvæ; the rearings of the larvæ of pure Gloveri were also, I think, a failure, only one correspondent having been successful; but some correspondents have not yet made the result of their experiments known to me. The larvæ of Samia cecropia, S. gloveri, and S. ceanothi, are very much alike; and hardly any difference can be observed in the first two stages. In the third and fourth stages, the larvæ of S. cecropia and S. gloveri are also nearly alike; the principal difference between these two species and S. cecropia being that the tubercles on the back are of a uniform color--orange-red, or yellow--while on Cecropia the first four dorsal tubercles are red, and the rest yellow. The tubercles on the sides are blue on the three species.
The larvæ of the hybrids Gloveri-cecropia were, as far as I could observe, like those of Cecropia, but I noticed some with six red tubercles on the back instead of four, as on Cecropia. They were reared on plum, apple, and Salix caprea; in the open air.
The larvæ of Samia gloveri were reared, during the first four stages on a wild plum-tree, then on Salix, caprea, and I reproduce the notes taken on this species, which I bred this year (1881) for the first time.
Gloveri moths emerged from the 15th of May to the end of June; five pairings took place as follows: 1st, 4th, 9th, 24th, and 26th of June. First stage--larvæ quite black. Second stage--larvæ orange, with black spines. Third stage--dorsal spines, orange-red; spines on sides blue. Fourth stage--dorsal spines, orange or yellow, spines on the sides blue; body light blue on the back, and greenish yellow on the sides; head, green; legs, yellow. Fifth and sixth stage--larvæ nearly the same; tubercles on the back yellow, the first four having a black ring at the base; side tubercles ivory-white, with a dark-blue base.
The above-mentioned American species, like most other silk-producing bombyces, were bred in the open air; but besides these, I reared three other species of American bombyces in the house, under glass, and with the greatest success. These are: Hyperchiria io, a beautiful species mentioned in my report for the year 1879; Orgyia leucostigma, from ova received on December 29, 1880, from Madison, Wis., which hatched on the 27th of May, 1881.
The third American species reared under glass is the following very interesting bombyx: Ceratocampa (Eacles) imperialis. The pupæ of this species are rough, and armed with small, sharp points at all the segments; the last segment having a thick, straight, and bifid tail. The moths, which measure from four to about six inches in expanse of wings, are bright yellow, with large patches and round spots of reddish-brown, with a purple gloss; besides these patches and round spots, the wings are covered with small dark dots. The male moth is much more blotched than the female, and although of a smaller size, is much more showy than the female.
With twenty-four pupæ of Imperialis I obtained nineteen moths from the 21st of June to the 19th of July; five pupæ died. Two pairings took place; the first from the evening of the 13th to the morning of the 14th; the second from the evening of the 15th to the morning of the 16th of July.
The ova, which are about the size of those of Yama-mai, Pernyi, or Mylitta, are rather flat and concave on one side, of an amber-yellow color and transparent, like those of sphingidæ. When the larvæ have absorbed the yellow liquid in the egg, and are fully developed; they can be seen through the shell of the egg, which is white or colorless when the larva has come out.
The larvæ of Imperialis, which have six stages, commenced to hatch on the 31st of July; the second stage commenced on the 7th of August; the third, on the 17th; the fourth, on the 29th of August; the fifth, on the 18th of September; and the sixth, on the 1st of October. The larvæ commenced to pupate on 13th of October.
The larvæ of this curious species vary considerably in color. Some are of a yellowish color, others are brown and tawny, others are black or nearly black. My correspondent in Georgia, who bred this species the same season as I did, in 1881, had some of the larvæ that were green. In all the stages the larvæ have five conspicuous spines or horns; two on the third segment, two on the fourth, and one on the last segment but one; this is taking the head as the first segment with regard to the first four spines These spines are rough and covered with sharp points all round, and their extremities are fork-like. In the first three stages they are horny; in the last three stages these spines are fleshy, and much shorter in proportion than they are in the first three stages. The color of the spines in the last three stages is coral-red, yellowish, or black. In the fifth and sixth stages the spine on the last segment but one is very short.
Here are a few and short notes from my book:
1st stage. Larvæ, about one-third of an inch; head, brown, shiny, and globulous.
2d stage. Larvæ, dark-brown, almost black; spines, white at the base, and black at the extremities; head shiny and light brown.
3d stage. Larve, fine black; head black; white hairs on the back; spines, whitish, buff, or yellowish at the base, and black at the extremities; other larvæ of a brown color.
4th stage. Larvæ, black granulated with white; long white hairs; horns, brown-orange with white tips; on each segment two brown spots. Spiracles well marked with outer circle, brown, then black; white and black dot in the center. Anal segment with brown ribs, the intervals black with white dots; head shining, black with two brown bands on the face, forming a triangle. Other larvæ in fourth stage, velvety black, with coral-red spines; others with black spines.
5th stage. Larvæ, entirely black, with showy eye-like spiracles, polished black head; other larvæ having the head brown and black. Larvæ covered with long white hair; spines black or red. No difference noticed between the fifth and sixth stages.
One larva on fourth stage was different from all others, and was described at the British Museum by Mr. W. F. Kirby as follows: "Larva reddish-brown, sparingly clothed with long slender white hairs, with four reddish stripes on the face, two rows of red spots on the back, spiracles surrounded with yellow, black and red rings; legs red, prolegs black, spotted with red. On segments three and four are four long coral-red fleshy-branched spines, two on each segment, below which, on each side, are two rudimentary ones just behind the head; in front of segment two are four similar rudimentary orange spines or tubercles; last segment black, strongly granulated and edges triangularly above and at the sides, with coral-red; several short rudimentary fleshy spines rising from the red portion; the last segment but one is reddish above, with a short red spine in the middle, and the one before it has a long coral-red spine in the middle similar to those of segments three and four, but shorter"
As soon as my Imperialis larvæ had hatched, I gave them various kinds of foliage, plane-tree, oak, pine, sallow, etc. At first they did not touch any kind of foliage, or they did not seem to touch any; and I was afraid I should be unable to rear them; but on the second or third day of their existence, they made up their minds and decided upon eating the foliage of some of the European trees I had offered them. They attacked oak, sallow, and pine, but did not touch the plane-tree leaves. In America, the larvæ of Imperialis feed on button-wood, which is the American plane-tree (Platanus occidentalis), yet they did not take to Platanus orientalis. After a little time I reduced the foliage to oak and sallow branches, and ultimately gave them the sallow (Salix caprea) only, on which they thrived very well. I was pleased with this success; as I had previously read in a volume of the "Naturalist's Library" a description of Ceratocampa imperialis, which ends as follows: "The caterpillars are not common, and are the most difficult to bring to perfection in confinement, as they will not eat in that situation; and, even if they change into a chrysalis, they die afterward."
Before I finish with C. imperialis, I must mention a peculiar fact. During the first stage, and, I think, also during the second, several larvæ disappeared without leaving any traces. I also saw two smaller larvæ held tight by the hind claspers of two larger ones. The larvæ thus held and pressed were perfectly dead when I observed them, and I removed them. My impression then was that these larvae were carnivorous, not from this last fact alone, as I had previously observed it with larvæ of Catocalæ when they are too crowded, but from the fact that some had disappeared entirely from the glass under which they were confined. I began to reduce their numbers, and put six only under each glass, so as to be able to watch them better. Whether I had made a mistake or not previously to this I do not exactly know; but from this moment the larvae behaved in a most exemplary manner, especially when they became larger. They crawled over each other's backs without the least sign of spite or animosity, even when they were in sleep, in which case larvæ are generally very sensitive and irritable, all were of a most pacific nature. It is, therefore, with the greatest pleasure that, for want of sufficient evidence, I withdraw this serious charge of cannibalism which I first intended to bring against them.
From what has been said respecting the rearing of exotic silk-producing bombyces, especially tropical species, it must have been observed that several difficulties, standing in the way of success, have to be overcome. The moths of North American species emerge regularly enough during the months of May, June, or July, but Indian and other tropical species may emerge at any time of the year, if the weather is mild, as has been the case during this unusually mild winter of 1881-1882. From the end of December to the present time (March 14, 1882) moths of four species of Indian silk-producers, especially Antheræa roylei and Actias selene, have constantly emerged, but only one or two at a time. These moths emerged from cocoons received in December and January last.
It is only when these tropical species shall have been already reared in Europe that the emergence of the moths will be regular; then they will be single-brooded in Northern or Central Europe, and some will very likely become double-brooded in Southern Europe. But when just imported the moths of these tropical species will always be uncertain and irregular in their emergence; hence the importance of having a sufficient number of cocoons so as to meet this difficulty, i.e., the loss of the moths that emerge prematurely or irregularly.
Before I conclude, I shall repeat what I already stated in a previous report, that the sending of live cocoons and pupæ from India and other distant countries to Europe, can easily be done, so that they will arrive alive and in good condition, if care be taken that the boxes containing these live cocoons and pupæ should not be left in the sun or near a fire (which has been the case before), and that they should at once be put in a cool place or in the ice-room of the steamer. The cocoons and pupæ should be sent from October to March or April, according to distance, and it is most important to write on the cases, "Living silkworm cocoons or pupæ, the case to be placed in the ice room."
By taking this simple precaution, live cocoons and pupæ, when newly formed, can be safely sent from very distant countries of Europe.
To continue these interesting and useful studies, I shall always be glad to buy any number of live cocoons, or exchange them for other species, if preferable.
ALFRED WAILLY.
110 Clapham Road, London, S.W.