BIRDS, CATERPILLARS, AND PLANT LICE. 117 



intelligent, industrious, and persevering of the smaller birds 

 will attack and devour them. When caterpillars are enclosed 

 in webs they are not quite so much exposed to the attacks 

 of birds as when they are feeding upon the foliage ; for many 

 birds lack either the intelligence, industry, or perseverance 

 exhibited by those that tear open the webs and hale forth the 

 inmates. Caterpillars get comparatively little protection, 

 however, by retreating into their webs, unless they feed at 

 night and remain clustered in the web during the entire day. 

 Even then they must run the gauntlet of some of the almost 

 crepuscular Thrushes and' Flycatchers, the Owls and Whip- 

 poor-wills. Those who tell us glibly that tent caterpillars 

 are never attacked by birds forget that these larva? are out 

 feeding upon the leaves during most of the day, where they 

 are just as much exposed to the attacks of birds as is any 

 other insect. It is true that at early morning and early 

 evening, a time when most birds are actively feeding, these 

 caterpillars are hidden away in their tents. Undoubtedly 

 this habit came through natural selection. Those that had 

 acquired the habit were more likely to escape the birds at 

 morning and evening than those that were out upon the 

 leaves at those times, and so, through generations, the habit 

 has become fixed. These caterpillars also may have some 

 immunity from birds by remaining in their tents during 

 some of the colder weather of early spring ; nevertheless, 

 the tents are not an infallible protection. Many species 

 of birds besides the Cuckoo tear open caterpillars' " nests." 

 Some do this merely to get at the larvae, others mainly to 

 procure web with which to bind together the other mate- 

 rials of which their own nests are composed. This cater- 

 pillar web is much used by birds for this purpose. Tent 

 caterpillars really have very little protection from birds 

 where the conditions are as they should be. 



For five years the birds have been mainly depended upon 

 to clear these larvse from the trees about my home, and 

 we have not in any year removed more than one or two 

 tents from the trees. In the spring of 1905 there were two 

 which appeared to have escaped the attacks of birds, and one 

 day, as we were about leaving home for the summer, I exam- 



