EXTERMINATING NOXIOUS INSECTS. 255 



large proportion of which may be exterminated with little 

 effort and expense, by trapping the depredators in small 

 bottles partly filled with very sweet water, to which a little 

 vinegar has been added. 



When the Tent -caterpillars leave their nests for the pur 

 pose of going to feed on the leaves, they travel upon the 

 upper side of the branches ; and each one leaves a thread of 

 silk behind it, which probably serves as a clue to direct it 

 back to the nest. The silken trails thus formed are at first 

 scarcely noticeable ; but they become very obvious after a 

 branch has been travelled upon for a considerable time. 

 Thus the caterpillar not only lives in a silken house, but 

 covers its roads w r ith a silken carpet. Like other larva?, 

 they shed their skins four times before arriving at maturi- 

 ty. When fully grown, they are about two inches in length, 

 and frequently two inches and a half long, fat and round. 

 The "American Entomologist," for which Fig. 95, p. 253, 

 was originally engraved, states that the eyes of this cater- 

 pillar have the appearance of very minute black points, 

 being ten in number, five on each side of the head. Their 

 position is best seen by holding the cast-off skin of a cater- 

 pillar towards the light and examining it through a magni- 

 fying-glass. Without claiming mathematical exactness, it 

 may be stated that four of them are situated in a curved 

 line, forming half a circle, of which circle the fifth occupies 

 the centre. Owing to the extreme minuteness of the eyes 

 of caterpillars in general, they were formerly overlooked, 

 and these insects were supposed to be blind. That they 

 possess the sense of seeing, however, and .that, too, at a con- 

 siderable distance, seems to be proved by the following ex- 

 periments. If a nest of these caterpillars be taken from a 

 tree and placed upon the ground several feet from it, they 

 will return to the tree in a direct line. In another experi- 

 ment a handful of caterpillars was placed in some tall grass 



