532 SILK-PKODUCIXG INSECTS. 



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 odour, 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 odour, this creature is thought to be the celebrated Cossus of the ancients, 

 a grab 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 colours 

 are of a very sober order, being greys 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 colour. 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 colour, 

 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 Bombycidse 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 Borne 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 conies 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 hank of soft 



