Nov. 1, 1S69.] 



HAIIDWICKE'S SCIENCE-GOSSIP. 



249 



LINA POPULI. 



WHILE botanizing in this neighbourhood Last 

 June, I came across a numberof larvae feeding 

 on poplar, not unlike the larva; of the common Lady- 

 bird, which I found to be gifted with a very curious 

 method of defence. On each side of the body runs 

 a series of papillae, or wartlike excrescences, from 

 each of which, when the animal is touched, issues a 

 drop of a yellowish milky fluid ; if the irritation is 

 not continued, the drops as quickly disappear. So 

 completely does the liquid retain its round form, and 

 so entirely is it absorbed again, that it has all the 

 appearance of a bladder, into which air is forced and 

 again withdrawn, until a touch dissipates the illu- 

 sion. But woe to the unlucky " searcher after 

 truth," who gets his hand besmeared with this most 

 abominable liquid; as Shaw long ago observed, 

 " the odour imparted by it is of so penetrating a 

 nature, that on handling the animal the smell will 

 often remain on the fingers throughout the whole 

 day." 



The specimens which I took home doubled or 

 trebled their size in a few days, and their colour 

 changed to a nearly pure white, the papillae alone 

 remaining black. By the middle of July each larva 

 had fixed itself by the tail end of the abdomen to 

 the surface of a leaf, and there remained head down- 

 wards, with the body slightly curved inwards, 

 gradually assuming a deep orange tint, as the elytra 

 of the enclosed beetle took their proper form. 



On the evening of the 25th, there issued forth 

 the handsome beetle (Lina populi), one of the 

 Chrysomelids.* At first the wings were of a dull 

 brick-colour, and only assumed their rich red hue 

 after an hour or two of exposure to the atmosphere. 

 The perfect auimal appears to be quite as destruc- 

 tive as its larva, being equally voracious, and 

 devouring the same food ; the only difference ap- 

 pears to be that the larva attacks the surface of the 

 leaf, whereas the beetle confines itself to the edge. 



Havre. W. W. Spicer. 



THE AMERICAN SILKWORM. 

 By L. Trouvelot. 



THE insect fauna of North America contains 

 several gigantic species of moths belonging to 

 the Lepidopterous family Bombycidae. This family 

 has long been known to spin when in the larval, or 

 caterpillar state, a cocoon which produces a large 

 amount of silk, with a fibre of the most delicate 

 texture, of great strength and of the most beautiful 

 lustre. Every one is familiar with the beautiful 



* The terminology of the Chrysomelids seems difficult to 

 settle. The older authors placed many of them under 

 Coccinella, to which they hear a strong family likeness. The 

 poplar - feeding species oscillate between four genera ■ 

 Linnaeus placed them in Chrysomela, Megerle in Lina, 

 Dillwyn in Melasoma, and Stephens in Timarcha. 



and delicate fabric made from the fibres spun by 

 that crawling repulsive creature, the Silkworm. 



Our country alone has eight or ten species of Silk- 

 worms. Two of these, Callosamia Promethea and 

 C. angulifera, feed on the lilac and wild cherry. 

 They spin a small elongate cocoon of so very dense 

 texture and so strongly gummed, that I have failed 

 in all my attempts to reel the silk from the cocoon. 

 These cocoons resemble very much those of Samia 

 Cynthia, or the Ailanthus Silkworm, recently 

 introduced into Europe from China, but the cocoon 

 is of a looser texture. Ptatysamia Euryale, P. 

 Columbia, and P. Cecropia feed upon many different 

 species of plauts ; they make a large cocoon, within 

 which is another cocoon, or inner layer, of an oval 

 form ; but as the larva in spinning the cocoon leaves 

 one end open for the exit of the moth, this prevents 

 the reeling of a continuous thread. The silk, though 

 quite strong, has not much brilliancy, and the worm 

 is too delicate to be raised in large numbers. 



The caterpillar of Tropeea Luna, the magnificent 

 green moth with the long tail-like expansion of the 

 hind wings, feeds upon the oak, sycamore, and other 

 trees, and spins an oval cocoon, •which, however, is 

 so frail and thin, and the fibre so weak, that it is 

 impossible to reel it. 



Practically, however, the larva of Telea Polyphe- 

 mus is the only species that deserves attention. The 

 cocoons of Platysamia Cecropia may be rendered of 

 some commercial value, as the silk can be carded, 

 but the chief objection, as stated above, is the diffi- 

 culty of raising the larva. The Polyphemus worm 

 spins a strung, dense, oval cocoon, which is closed 

 at each end, while the silk has a very strong and 

 glossy fibre. 



Por over six years I have been engaged in raising 

 the Polyphemus worm, and here present the fol- 

 lowing imperfect sketch of the progress made from 

 year to year in propagating and domesticating these 

 insects from the wild stock. 



In 1S60, after having tested the qualities of the 

 cocoons of the different species of American Silk- 

 worms, I endeavoured to accumulate a large num- 

 ber of the cocoons of the Polyphemus moth, for the 

 future propagation of this species. At first the 

 undertaking seemed very simple, but who will ever 

 know the difficulties, the hardships, and discourage- 

 ments which I encountered ! This worm having 

 never been cultivated, of course its habits were 

 entirely unknown, though ; all success in my 

 undertaking depended very much upon that know- 

 ledge. However, I was not discouraged by the 

 difficulties of the task. The first year I found only 

 two caterpillars. The chance of their being each a 

 male and female was very small, and it was another 

 question whether the two sexes would come out of 

 the cocoon at about the same time for the fecunda- 

 tion of the eggs. So success was very doubtful. 

 Spring came, and with it one of the perfect insects ; 



