424 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1920. 



A. "W. Anthony states 27 that — 



In southern California the passion vine is everywhere infested by a red but- 

 terfly (Agraulis vanillae), the larvae of which feed extensively if not entirely 

 upon this plant. So great is the damage that plants are often completely de- 

 foliated and become so unsightly that in some regions many have destroyed 

 their vines and replaced them with other species, less desirable, perhaps, but 

 less apt to breed a horde of pests. 



Not long since I called on a friend living in the suburbs of San Diego who 

 had a large number of unusually thrifty passion vines climbing over his fence. 

 Upon inquiring the reason of their freedom from what I considered an inevitable 

 pest he informed me that a pair of roadrunners (Geococcyx californianus) had 

 for several months paid daily visits to his vines, climbing through them in all 

 directions until the last caterpillar had been captured. 



Robert Ridgway, America's foremost ornithologist, gives the fol- 

 lowing account of the extirpation of a colony of caterpillars {Datana 

 integerrima) on black, walnut at his former home in Brookland, 

 District of Columbia: 



We first noticed the caterpillars something like two weeks ago, our attention 

 being attracted to them by noticing several branches which had been stripped 

 of their leaves. We then discovered the caterpillars in clusters on the twigs 

 and foliage, and a little later a compact mass of them, about a foot long by 6 

 inches wide, on the bark of the trunk, a foot or so from the ground. Within a 

 day or two of our first discovery of the pests we saw a yellow-billed cuckoo in 

 the tree busily engaged in eating the caterpillars. Later this was joined by 

 another (probably the mate), which, however, only made occasional visits to 

 the tree, its time being doubtless mainly occupied with incubating or brooding. 

 The other cuckoo practically lived in the tree, being very seldom absent, even 

 for a short time, and was so persistent in his destruction of the caterpillars 

 that whenever one fell to the ground he would immediately follow it and then 

 dispatch and devour it; and later, when few were left on the tree, we saw 

 him carefully searching the ground beneath. The results of the work of these 

 two cuckoos (principally one of them) was that within a week the colony of 

 caterpillars was absolutely exterminated, and I have not been able to find 

 one in the neighborhood. (July 30, 1906.) 



Smooth caterpillars are eaten by almost all birds and usually in 

 considerable numbers. None are more suitable for bird food than 

 canker-worms, a fact that has in many cases led to great reduction in 

 numbers of these insects. O. E. Bremner, of the California State 

 Horticultural Commission, communicates the following observations 

 on birds and canker-worms to the Biological Survey (Mar. 16, 1908) : 



In one district, Dry Creek Valley, Sonoma County, there has been a threatened 

 invasion of the prune trees by spring canker-worms several times, but each time 

 the blackbirds (Brewer's) come to the rescue and completely clean them out. 

 I have often seen bands of blackbirds working in an infested orchard. They 

 work from tree to tree, taking them clean as they go. If a worm tries to escape 

 by webbing down they will dive and catch him in midair. 



Mr. Ehrhorn tells me of an incident near San Jose where the canker-worms 

 were badly infesting a prune orchard, and when they commenced to irrigate 

 the land the blackbirds seemed to be attraced by the water, and inside of thi*ee 

 days there was not a single worm left. 



27 Auk, XIV, p. 217, 1897. 



