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July, 1915 WOODPECKERS O1' THE ARIZONA LOWLANDS 157 ing but the difference was too slight to be sure of in measuring. Of eighteen holes measured, the average diameter was 1.95 inches; the largest was 2.25 inches and the smallest 1.87 inches. The deepest hole was 16 inches, with the entrance 2 inches in diameter. The shallowest one was 9 inches, with entrance a little less than 2 inches in diameter. The average depth of holes measured was a lit- fie more than 12 inches. Many of the holes were not exactly circular, there being a difference of from ? to nearly ?/2 inch between the long and the short diameter if it be allowable to use the term in that way. Usually the nest hole runs straight in for a short distance before turning downward, the dis- rance seemingly depending on the texture of the wood. In one case the hole went straight back for nine inches -?/; ? .- before turning downward. It was in a big cottonwood :?. stump, and the bird excavat- ed horizontally until decayed wood was reached, when the hole turned downward. This was an extreme case, as the depth horizontally is usually about three inches. In the giant cactus it varies accord- ing to the diameter of the trunk, the smaller the trunk the less distance before turn- ing downward. The ?ftness of the material is not a fac- tor as it is the .same in small and large trunks. In only ?' ? two cases have I found nest ?, ? holes that penetrated through ?1?: the ribs of the cactus into the inner pith. In both cases Fig. 57. NEST CAVITY OF GILA WOODPECKER, the tn?nk was too small to rao? GIANT CACTUS TRL'NK, SHOWING THE furnish room for the nest be- IIARDENED LINING RE.MOVED FRO?I THE PULPY STALK. tween the outside and the-- ribs. The holes are dug in the ?ft pulp of the cactus, and' the raw surface be- comes calloused, as it were, forming a tough woody lining to the hole, which persists when the rest of the pulp decays. In this way the nest holes may be found intact, the hole being outlined by the hardened pulp, while the surround-