SPINNERS AND WEAVERS 7 



leaf are covered with fragments of leaves and 

 other vegetable matter to make it less obtrusive. 

 But the point to which we desire to call attention 

 is that the ant lines these nests with silk of its 

 own manufacture, and of a texture similar to spiders' 

 web. 



The chief spinners, however, are the caterpillars 

 of the butterflies and moths, especially of the 

 moths. As a rule the spinning of butterfly cater- 

 pillars is restricted to the fabrication of a silken pad, 

 into which the terminal hooks of the chrysalis 

 become attached, and of a girdle around what we 

 may term the waist of the chrysalis. There are 

 exceptions, as we shall show. The fluid silk is 

 produced by two large glands, one on each side of 

 the body, whose ducts unite and are continued 

 externally as the spinneret, which is a point on the 

 middle line of the lip, differently developed in the 

 various families and species. The glands are of 

 simple structure, and vary in size according to the 

 amount of silk-production required by the species. 

 In some of the moth-caterpillars that elaborate 

 thick cocoons their length and weight are con- 

 siderable : the Silkworm, for instance, possesses a 

 pair of silk-glands {sericterid) each measuring five 

 times the full length of the body. 



This length is exceeded in some other species. In 

 the full-grown Silkworm their weight equals two- 

 fifths of the insect's total weight. This is not sur- 

 prising when one considers the great length of thread 

 that is produced in the weaving of the cocoon. 



