THE SILKWORM ITS FORM AND LIFE HISTORY. 



the divisions cannot be traced on the back, the skin there being 

 puckered and wrinkled. The diameter of the body does not 

 long remain uniform throughout, but the part immediately behind 

 the head soon becomes somewhat swollen. This is perfectly 

 natural, and is no indication of anything wrong with the part in 

 question. On the underside we find some legs, but we see that 

 they are of two kinds, and situated in two different places. 

 Attached to the segments immediately behind the head are three 

 pairs of what look like little hooks one pair, a right and a left 

 hook, on each of three successive segments. These are the true 

 legs. Farther back there are five pairs of totally different organs, 

 situated, one pair on the last segment, and the other four on 

 segments six to nine, the tenth and eleventh carrying none. 

 These are the claspers, or prolegs, as they are sometimes called, 

 the prefix " pro " implying here substitution, and not position- 

 " for ' : and not " fore " ; they do duty for legs, but are only a 

 temporary expedient, and no trace of them is visible when the 

 creature reaches its adult condition. The examination of the 

 structure of these locomotive organs, as well as of the mouth 

 organs, we had better postpone till the caterpillar has grown 

 larger, when it may be much more easily effected ; and indeed, 

 many of the points noticed above will be more conveniently 

 observed at a later stage. In its blackish colour and hairy skin, it 

 differs totally from what its future appearance is to be. 



As we shall have occasion, in a subsequent chapter, to refer to 

 the food and the method of supplying it, we need not particularize 

 here, but simply say that the little orphan, for such it is, having 

 lost both its parents months before it was hatched, soon sets to 

 work on the food it finds ready to hand, and rapidly increases in 

 size, filling out its loosely fitting skin, and becoming reddish- 

 brown in colour, till in about five or six days' time, it has reached 

 the limits of expansibility of its first garment, for the skin does 

 not grow with the rest of the body, and something must be done 

 to provide for the increase in bulk that has yet to be accomplished. 

 The grub has now passed through what is technically called its 

 " first age," and before entering upon the second, it has to undergo 

 the somewhat trying process of " moulting," or casting its skin. 

 Succeeding ages are passed through with similar regularity, though 

 the exact duration of each will vary with the temperature, and it 

 will generally be found by amateurs that the times here mentioned 

 will be slightly exceeded. 



As the period of the change of skin approaches, the silkworm 

 loses its appetite, and soon ceases to eat altogether. It then takes 

 up a position at some chosen spot, raising the anterior part of 



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