FOOD OF WARBLERS 29 



Beetles (Coleoptera) form a varying part of the food of Warblers. 

 While a few beneficial species are eaten, the vast majority taken 

 are believed to be either neutral or injurious. The useful lady- 

 bugs (Coccinellidae) apparently are seldom eaten. The tiger beetles 

 and the larger useful ground beetles ( Cicindelidae and Carabidse) are 

 not much sought by Warblers. 



Many of the injurious bark beetles and other boring beetles are 

 greedily eaten. Bark beetles (Scolytidae) are among the most 

 insidious and deadly enemies of trees. They often complete the 

 destruction of trees that have been defoliated by caterpillars. 

 Unable, as they usually are, to live in the most thrifty and vigorous 

 trees, a tree is no sooner weakened by the loss of its leaves, than 

 these beetles are attracted to it. Their eggs are soon deposited 

 and the resulting larvae bore away among the vital tissues of the 

 tree along the inner surface of the bark. If their increase is not 

 checked, a year or two of their work is sufficient to destroy the 

 noblest trees of the forest. The Warblers, however, attack these 

 borers as they mature and emerge from their burrows in the pair- 

 ing season. The Black and White Warbler, which in summer 

 takes the place so well filled in winter by the Brown Creeper, prob- 

 ably leads in the destruction of bark beetles, but many other 

 species eat them, and thus the Warblers again come to the rescue 

 of the trees. 



Warblers are not only useful in woodland by destroying bor- 

 ers, they are valuable also in orchards. Professor S. A. Forbes 

 found that fifteen Warblers shot in an orchard infested by canker 

 worms in Illinois, had all eaten Cerambycid beetles, or borers, to 

 the amount of ten per cent, of their stomach contents. Other 

 important elements of the food of Warblers at times are the 

 destructive click beetles and weevils. Leaf-eating beetles also are 

 eaten. 



Many Hymenoptera are taken by the flycatching Warblers, 

 such as the Redstart and other species that capture much of their 

 food on the wing. Some of the wasps and bees taken are bene- 

 ficial, but they are probably most useful when kept within proper 

 bounds by the birds. At times considerable numbers of hymen- 

 opterous parasites are taken. 



It is probable, however, that the larger numbers of these useful 

 insects are found in the stomachs of Warblers only when the para- 

 sites are unduly abundant. A surplus of these insects is of no 



