667 



EOMBTCID^E. 



BOMBYCILLA. 



558 



Some of the species fly very rapidly, and make their appearance in 

 the day-time as well as in the evening. The caterpillars of most of 

 the species are hairy (some produce great irritation to the hand when 

 touched), and assume the pupa state in a cocoon spun for its protection. 

 The pupa is simple. 



One of the most interesting of the family is the Bonibyx Mori, well 

 known as the moth to which the Silkworm turns. This species which 

 was originally from China is of a white or cream colour, with a brown 

 fascia and two or more waved lines of a deeper colour crossing the 

 upper wings. In this country the eggs of this moth hatch early in 

 May ; the caterpillar or silkworm is at first of a dark colour, but soon 

 becomes light, and in its tints much resembles the perfect insect, a 

 circumstance common in caterpillars. Its proper food is the mulberry, 

 though it will likewise eat the lettuce and some few other plants ; on 

 the latter however it does not thrive equally well, and the silk yielded 

 is of a poor quality. 



a and 6, llombyx J/ori; e, the eggs ; d, the pupa; e, silkworm or caterpillar. 



The Silkworm is about eight weeks in arriving at maturity, during 

 which period it changes its skin four or five times. When about to 

 cart its skin it ceases to eat, raises the fore part of the body slightly, 

 and remains in perfect repose. In this state it is necessary that it 

 should continue for some little time, in order that the new skin, which 

 is at this time forming, may become sufficiently mature to enable the 

 caterpillar to burst through the old one. This operation, which is 

 apparently one of considerable difficulty, is performed thus : the 

 fore part of the old skin is burst ; the silkworm then by continually 

 writhing its body (but not moving from the spot) contrives to thrust 

 the skin back to the tail, and ultimately to disengage itself altogether 

 this last part of the operation however is the most difficult, since il 

 is no uncommon occurence for them to die from not being able to 

 disengage the last segment of the body from the old skin. 



Those who have reared silkworms must have observed how large 

 the head is in proportion to the body in those which have just changec 

 their okins; this circumstance is worthy of observation, for in it wil" 

 be found a most beautiful contrivance. 



When the larva of an insect has just changed its skin, every part is 

 soft, and in many cases (such as caterpillars) the greater portion o 

 the body still remains in this flexible state ; but the skin of the head anc 

 some few other parts in all instances soon become hardened, after which 

 it never grows. The same happens with those larvae which have thi 

 body in a great measure covered with hard plates, which circumstano 

 leaves no parts to enlarge but such as are flexible. In the instance o 

 a caterpillar the body increases in size rapidly after change of skin 

 but the head it will be observed does not enlarge, and although the 

 body may have increased very much it does not appear that the skin 

 has grown ; it seems only to be stretched with the increase of size o 

 the inner parts. In the case of those larvae which have the body 

 covered with hard plates, it is the skin between the plates that stretche 

 to allow of growth in the inner parts, so that just before changing skin 

 all the plates are considerably separated. 



From the above wo conclude that the external covering of insect* 

 does not grow at all, except at the time of repose previous to th 

 casting off the old skin, after which operation the head and those part 

 which soon become hard are sufficiently grown to last until the nex 

 change ; and also that the soft parts of the external covering wii 

 ^retching to a certain extent and no further when it become 

 necessary that they should change that covering for a larger one 



Vith respect to the silkworm and other caterpillars, an unobserving 

 erson would not readily understand how the head, which is much 

 arger than the one the case of which has just been cast off, can have come 

 ut of it ; but if the silkworm be examined just before it is about to 

 hange its skin, it will be seen that such ig not exactly the case, for 

 >art of the new head may be seen thrust out behind the old one, so 

 hat the fore part only is inclosed by the latter. 



When full grown the silkworm commences spinning its web in some 

 onvenient spot, and as it does not change the position of the hinder 

 >ortion of its body much, but continues drawing its thread from 

 arious points and attaching it to others, it follows that after a time 

 ts body becomes in a great measure inclosed by the thread. The 

 work is then continued from one thread to another, the silkworm 

 moving its head and spinning in a zigzag way, bending the fore part 

 of the body back to spin in all directions within reach, and shifting 

 -he body only to cover with silk the part which was beneath it. As 

 .he silkworm spins its web by thus bending the fore part of the body 

 >ack, and moves the hinder part of the body in such a way only as 

 to enable it to reach the farther back with the fore part, it follows 

 that it incloses itself in a cocoon much shorter than its own body, for 

 soon after the beginning the whole is continued with the body in a 

 >ent position. From the foregoing account it appears that with the 

 most simple instinctive principles all the ends necessary are gained. 

 !f the silkworm were gifted with a desire for shifting its position 

 much at the beginning of the work it could never inclose itself in a 

 cocoon ; but by its mode of proceeding, as above explained, it incloses 

 tself in a cocoon which only consumes as much silk as is necessary 

 to hold the chrysalis. 



During the time of spinning the cocoon the silkworm decreases in 

 .ength very considerably, and after it is completed, it is not half its 

 original length ; at this time it becomes quite torpid, soon changes its 

 skin, and appears in the form of a chrysalis. The time required to 

 complete the cocoon ia about five days. In the chrysalis state the 

 animal remains from a fortnight to three weeks ; it then bursts its 

 case and comes forth in the imago state, the moth having previously 

 dissolved a portion of the cocoon by means of a fluid which it 

 ejects. 



The moth is short-lived ; the female, in many instances, dies almost 

 immediately after she has laid her eggs ; the male survives her but a 

 short time. 



The silkworms, which are most extensively reared for the purpose 

 of producing silk [SiLK, in ARTS AND Sc. Div.], are liable to many 

 diseases, and none have been more destructive than that called 

 muscardine. This disease attacks the caterpillar when about to enter 

 the chrysalis state. It is always attended with the development 

 within the body of a minute fungus closely resembling our common 

 mould. It is probable the fungus only attacks those worms which 

 are predisposed to disease, but in certain seasons this fungus has been 

 so extensively developed as to lead to the supposition that it produces 

 the disease itself. It is very certain that, when this fungus is 

 prevailing and its spores are introduced into the body of the silk- 

 worm, it becomes rapidly diseased and dies. The fungus spreads 

 internally before the death of the worm and afterwards it shoots 

 forth from the surface of the skin. The chrysalis and moth will have 

 the disease if inoculated with the fungus, but it only occurs sponta- 

 neously on the caterpillar. 



BOMBYCILLA, a genus of Tooth-Billed Birds (Dentiroiires). Cuvier 

 places the genus among the Dentirostral genera of his second order 

 Paasereaux ; Latreille also arranges it under that order, but does not 

 allow it to belong to the Dentirostres, and classes it among his first 

 family, that of the Broad-Billed Birds (Latirostrea). Temminck, con- 

 sidering it to be an omnivorous bird, finds a place for it under the 

 name of Bombycii'ora, in his second order Omnivores. Vieillot's 

 second order (Kylricola) contains two tribes; and in the sixteenth 

 family (Baccivori) of the second tribe (Anigodactyli), the genus in 

 question will be found. Vigors places it in the second tribe Denti- 

 rottret of his second order, Inaessores, or Perching Birds ; and after some 

 hesitation, and expressing his doubt whether its natural situation is 

 not hi the family Merididie, is inclined to arrange it provisionally 

 among the Pipridfe, his last family of Dentirostres, Bonaparte makes 

 it a genus of his family Sericati. Swainson, in the ' Fauna Boreali- 

 Americana,' arranges it under his -Bombycillina;, n subfamily belonging 

 to the aberrant group of his A mpelida?, or Fruit-Eaters ; but in giving 

 his table of Ampelidre, he expresses considerable doubts on the true 

 nature of the aberrant divisions. Linnaeus at one time made it a 

 Butcher-Bird (Lanius), and afterwards an Ampelia. Brissou classed it 

 among the Thrushes (Turdus), and Illiger among the Crows (Corrus). 

 The birds of this genus are known by the English names of Wax- 

 Wings or Waxen-Chatterers ; and the following are the principal 

 generic characters according to Temminck : Bill short, straight, 

 elevated ; upper mandible curved towards its extremity, with a 

 strongly marked tooth ; nostrils basal, ovoid, open, hidden by strong 

 hairs directed forwards ; feet, with three toes before and one behind, 

 the exterior toe connected (soudc!) with the middle one; wings 

 moderate, the first and second quills longest. 



Only three species have been recorded. The first has a wide 

 geographical range ; the second is confined to North America ; and 

 the third is Oriental. 



