224 



THE INSECT WOELD. 



the silk- producing organ is continued in an enlarged portion DE, 

 which is the reservoir of the silky matter. To the extremity, E, 

 of this reservoir, is attached another capillary tube, E F. These two 

 capillary tubes, proceeding from the two glands, 

 unite together like two veinous trunks, as the 

 plate shows, in one single, short canal, F, which 

 opens in the mouth of the worm, at its under-lip. 

 It is in the narrow hinder tubes that the silky 

 matter is formed. It collects in the swollen part 

 D E, which is, properly speaking, the reservoir ; 

 and remains there in the glutinous state. Having 

 reached the capillary tubes, it begins to assume 

 consistency, and forms two threads, which are 

 united together at the point of junction of the 

 tubes, and come out through the orifice, with the 

 appearance of a single thread, to be conducted and 

 directed by the animal to those points it has 

 selected. 



It was hoped that by taking from the body of 

 the worm the viscous matter contained in the 

 glands, silk could be formed. But this hope was 

 disappointed. It was found possible, it is true, 

 to take the silk out ; to draw it out into threads 

 more or less fine ; but up to this time it has only been possible in 

 this way to obtain a matter which, when dried, more or less resem- 

 bles catgut, and is easily enough spoilt by water. 



The viscous substance contained in the glands must then be 

 elaborated by the insect itself. When it arrives in the conduit 

 common to the capillary tubes, under the form of a thread, it is 

 impregnated with a sort of varnish, which is poured into them 

 from two neighbouring glands. The varnish unites the two 

 threads into one single thread, and imparts to it the brilliancy of 

 silk, and the property of resisting the action of water. It is 

 during the last phases of the worm's development that the silky 

 matter becomes abundant in the glands. At this period, the 

 animal eats much ; and it is certain that the substance to be con- 

 verted is furnished by the leaf of the tree on which the insect 

 feeds. 



