2O SILKWORMS. 



It is now sufficiently large to permit of our easily examining 

 certain niceties of structure that we have hitherto omitted, but 

 it will still be useful to employ a hand-lens to assist in this 

 examination. Commencing with the head, we notice that this 

 is a rounded, polished surface, divided into two parts by a line 

 down the middle. These large polished pieces are sometimes, 

 from their glistening appearance, supposed to be eyes, but that 

 is an entire mistake. There are eyes, it is true, but they are 

 minute, and are placed very near the jaws an extremely signifi- 

 cant arrangement. They will be seen at each side as a number 

 of tiny rounded and glistening black spots. They do not appear 

 to be of any very great use to their owner, who, though not 

 absolutely blind, can yet apparently do little more than distinguish 

 light from darkness. But this is no great drawback, for it will 

 spend the whole of its caterpillar life within an area of a few square 

 inches, and it needs to see only one thing, viz., mulberry leaves, 

 and these its human owner will provide it with. 



Between the two polished halves of the head below is a 

 triangular space called the dypens, and below this is a sort of lid 

 stretching across from one side to the other, and hinged above to 

 the clypeus, so as to be movable outwards upon its own upper 

 edge. This is called the labnun, or upper lip. It partially con- 

 ceals the very powerful jaws, or mandibles ; which, to a creature 

 so devoted to eating, are among the most important organs it 

 possesses. They are a pair of short, but broad and very strong 

 blades, jointed to the head just behind the labrum, working side- 

 ways and meeting in the middle, like a pair of shears. The edges 

 which meet are furnished with pointed projections or teeth, so 

 that when the mandibles are closed upon the leafy food, the latter 

 is nipped off in little pieces by these teeth. Here we may notice 

 that these jaws are, in every possible respect, the exact opposite 

 of our own. Ours are placed inside the mouth, where they are 

 sheltered by fleshy lips, those of silkworms are outside, and there 

 are no such things as fleshy lips at all. Ours have their hard 

 parts inside, and are covered by the tender, fleshy gums ; theirs 

 have the hard parts outside, and gums are totally absent. The 

 upper jaw of a human being is fixed, and the lower jaw moves 

 vertically towards it, and if he were to eat a leaf, he would place 

 it horziontally between the two. The jaws of silkworms are both 

 of them movable, the movement is lateral, and when they eat a 

 leaf, it is placed vertically between the jaws. 



The task of getting the food into the mouth is not left to the 

 mandibles alone; another pair of jaws comes to their assistance 

 a pair of manipulators rather than biters. They are placed behind 



