53 2 SILK-PRODUCING INSECTS. 



smooth and shining, mostly of dull mahogany-red tinged with ochreous yellow, and 

 having a large oval patch of chestnut on the back of each segment. It is gifted with 

 a curiously wedge-shaped head, and its muscular power is enormous, as may be proved 

 by actual experiment during the life of the creature, or inferred from the marvellous 

 arrangement of muscles which are made visible upon dissection. 



It exudes a liquid of powerful and fetid odor, thought by some to resemble the 

 unpleasant effluvium exhaled by the he-goat. Its influence extends to a considerable 

 distance, and a practised entomologist will often detect the presence of a Goat-moth 

 caterpillar simply by the aid of the nostrils. In spite, however, of the repulsive aspect 

 and unpleasant odor, this creature is thought to be the celebrated Cossus of the an- 

 cients, a grub which was found on trees, and, when dressed after some particular 

 fashion, was looked upon as a very great dainty. The whole structure of the caterpillar 

 is very interesting, and has been thoroughly worked out in the elaborate treatise by 

 Lyonnet, to which the reader is referred for further information on the subject. 



The caterpillar passes three years in the larval stage of existence, and when the time 

 approaches for its change, it ceases to burrow, and scoops out a convenient cell in the 

 tree, lining it with a fabric of mixed wood-scrapings and silken threads. Before it 

 emerges from this retreat, it pushes itself through its burrow like a sweep ascending a 

 chimney, protrudes about half of the body, and then emerges from the chrysalis shell, 

 which it leaves within the burrow. The texture of the wings is soft and downy, and 

 the colors are of a very sober order, being grays and browns of different tones, with a 

 very little ochreous yellow and a number of narrow black waving streaks. 



THE last figure in the illustration represents the WOOD LEOPARD-MOTH, a very 

 prettily marked insect, though without the least brilliancy of color. The caterpillar of 

 this insect feeds upon the interior of many trees, seeming to prefer the wood of the 

 apple, pear and other fruit trees. It is a naked, fleshy-looking larva, of a light yellow 

 color, and having a double row of black spots upon each segment. Like the goat- 

 moth, it prepares a cocoon-like cell when it is about to take the pupal form, but the 

 lining is of stronger materials, cemented firmly together with a glutinous substance 

 secreted by the insect. The moth is seldom seen until July, and is tolerably plentiful 

 in some places, appearing to be decidedly local and rather intermittent in its visits. 



THE family of the Bombycidae includes several insects of inestimable value to man- 

 kind, the various silk-producing moths being included in its ranks. The common silk- 

 worm is too familiar to need any notice, but as it is not generally known that upwards 

 of forty silk producing moths exist in different parts of the world, a short history will 

 be given of some of them, together with a figure and a brief description of one of the 

 finest species. 



All these insects secrete the silk in two large intestine-like vessels in the interior, 

 which contain a gelatinous kind of substance, and become enormously large just before 

 the caterpillar is about to change into a pupa. Both the silk organs unite in a common 

 tube at the mouth, technically called the spinneret, and through this tube the semi-liquid 

 is ejected. As soon as it comes into contact with the air it hardens into that soft, 

 shining fibre with which we are so familiar. If a single fibre of silk be examined 

 through a good microscope, it will be seen to consist of two smaller fibres laid parallel 

 to each other, like the barrels of a double gun, this structure being due to the double 

 secreting vessels. The goodness of silk chiefly consists in the manner in which these 

 semi-fibres are placed together. Silk-worm " gut," as it is called by anglers, is made 

 by steeping the caterpillars in strong vinegar for a time, and then pulling them suddenly 

 until they elongate into the well-known threads to which hooks are attached. 



The caterpillar employs the silk for the purpose of constructing a cocoon in which it 

 can lie until it has assumed the perfect form ; and proceeds with wonderful regularity and 

 dispatch in its work, its head passing from side to side, always carrying with it a thread, 

 and the cocoon being gradually formed into the oval shape which it finally assumes. 

 The few outermost layers are always rough and of poor quality ; these are stripped 

 off, and the end of the thread being found, it is fastened to a wheel, and spun off into a 



