26 FOOD OF WOODPECKERS OF UNITED STATES. 



which eat more of the pests of the forests than do the three-toed 

 woodpeckers; and while we have no doubt determined the principal 

 food factors, there are many minor questions for the solution of 

 which additional material is necessary. 



In the first analysis the food divides into 88.69 per cent of animal 

 matter to 11.31 of vegetable for arcticus, and 94.06 per cent of animal 

 to 5.94 of vegetable for americanus. The largest item with both 

 species is wood-boring coleopterous larvae. These amount to 64.25 

 per cent with arcticus and 60.66 with americanus. Caterpillars, 

 which in this case are mostly wood-boring species, amount to 12.88 

 and 14.45 per cent for the two bird respectively. The total of wood- 

 boring larvae, including both caterpillars and beetles, is 77.13 per 

 cent for arcticus and 75.11 per cent for americanus, or more than 

 three-fourths of the food of each species. Stomachs containing 15 

 to 20 of these grubs are very common, and one held 34. Probably 

 the stomach is filled several times each day, and it does not seem 

 unreasonable to assume that a bird will eat 50 of these insects every 

 24 hours for 6 months and at least 25 daily for the other half of the 

 year. At this rate one bird will annually destroy 13,675 of these 

 destructive grubs. If this assumption be true, the birds of these 

 two species must destroy an immense quantity of wood-boring insects, 

 even if they do not cause any perceptible diminution in their num- 

 bers. Beetles other than wood-borers amount to 3.41 per cent for 

 arcticus and 10.39 for americanus. A considerable proportion of 

 these were weevils, including quite a number of engravers (Scoly- 

 tidse). They are, however, eaten so irregularly as to indicate that 

 they are taken only incidentally and are not sought, as are the wood- 

 boring grubs. Ants constitute 6.35 per cent of the food of arcticus 

 and 8.29 of that of americanus. None of these were taken in winter, 

 and most of them were eaten in spring and summer. The Picoides 

 do not belong to the ant-eating group of woodpeckers. A few other 

 insects and spiders amount to less than 1 per cent for each species 

 and make up the remainder of the animal food. 



Vegetable food. Vegetable matter constitutes 11.31 per cent of the 

 stomach contents of arcticus and 5.94 per cent of that of americanus. 

 It can all be included in four items: Fruit, mast, cambium, and 

 rubbish. Fruit skins were found in only 1 stomach of americanus 

 and mast in bat 1 stomach of arcticus. Cambium was found in 10 

 stomachs of arcticus and 8 of americanus. This indicates that these 

 birds do some pecking at the bark of living trees for other purposes 

 than getting insects, but no complaints have yet been made, from 

 which we infer that little or no damage is done; in fact the amount 

 contained in the stomachs is not large, a little less than 10 per cent. 

 Rubbish, consisting principally of rotten wood, was found in 9 



