INSECTA. 163 



elastic threads, which facilitate the escape of the enclosed 

 insect, but prevent the entrance of intruders. There are 

 several smaller species belonging to this family. 



The Silk Worm (bombyx mori) is yellow-white, with 

 broad, brownish transverse stripes on the superior wings. 

 The caterpillar is pale gray, and called the silk worm. 

 The silken material of which this worm makes its regular 

 cocoon, is a glutinous mass of threads spun from the 

 mouth ; these are very tough, can not be dissolved in 

 hot water, and are easily dried in the air. The silk 

 worm came originally from China, where the culture of 

 silk was practiced from very remote ages. Sixteen hun- 

 dred years ago silk was so dear that the wife of the 

 Roman emperor was refused a robe of silk, as being too 

 expensive a luxury. In the middle ages the eggs of the 

 silk worm were first brought to Europe. In 555, some 

 Greek missionaries, during the reign of Justinian, having 

 penetrated to the northern provinces of China, procured 

 some eggs, which they concealed in hollow canes, and 

 brought to the emperor. They were hatched by the 

 heat of a dunghill, and the larvae grew, prospered, and 

 formed the foundation of the race in Europe. The cul- 

 ture of silk, however, was but little attended to before 

 the year 600. The caterpillars of the bombyx feed on 

 the leaves of the white mulberry ; should these fail they 

 will eat garden lettuce, alder or pear tree leaves, which 

 must be given them twice every day and perfectly dry. 

 The little larvae are at first brown or dark gray, but 

 gradually grow whiter. The skin is cast several times ; 

 they are very tender and so extremely susceptible of 

 cold, that in spring it is necessary to keep them in warm 

 rooms. When ready for the transitionary state, they ai*e 

 fed on the leaves of mugwort. They first spin a 



