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kill living trees, but the horntail , generally follows injury of some 

 kind. Within the tree trunk there is not the safety from enemies 

 which one might anticipate. A large number of wood-inhabiting im- 

 mature insects are footless, and have relatively small powers of loco- 

 motion. Their burrows are relatively small, so that when an enemy 

 once gains admission it can easily secure the owner. Tree trunks 

 infested with horntails often have. a large number of females of Tha- 

 lessa on them. I have caught them literally by the handful in such 

 places. Many other parasitic Hymenoptera are easily taken upon 

 trees infested by boring larvae if watched carefully during the warm 

 parts of the day. Schwarz ('82) has called attention to a number 

 of beetles which live in the burrows of wood-boring insects. These 

 burrows may be invaded, not only while yet inhabited by their mak- 

 ers, but also after their abandonment. To find an insect in a burrow 

 is therefore not proof that the insect made it. A predaceous larva 

 which is reported to destroy bark- and wood-boring larvae is Alaus 

 oculatus L. (PI. XVI, figs, i, 2, and 4). I have taken this larva in 

 the woods at White Heath, 111., May 26, and the beetle at Savanna, 

 111., May 30. The beetle was taken at Bloomington, 111., March 23 

 (A. B. Wolcott) ; in its hibernating cell in a rotten log in the Cot- 

 tonwood forest October 8 (No. 489, C. C. A.) ; and — an immature 

 larva — in the Brownfield woods May 23, Urbana, 111. Both the larva 

 and the beetle hibernate in logs. Hopkins ('04, p. 42) says of the 

 larva: "As a larva [it] preys upon numerous species of bark and 

 wood-boring insects in deciduous trees." Currie ('05, p. 102) says: 

 "The larvae prey upon and do much toward preventing the increase of 

 several of the destructive flat-headed borers (Buprestidce) in decidu- 

 ous trees." Snyder ('10, p. 8) reports the larva of Alaus sp. "espe- 

 cially injurious" to decayed poles, and Lugger ('99, p. 130) states 

 that they live largely upon insects found in decayed wood. Evi- 

 dently the food habits of these larvae need investigation. Probably 

 other predaceous elaterid and trogositid larvae live in our trees. 

 Other predaceous beetles on trees are the following, taken at Bloom- 

 ington: Chariessa pilosa Forst., July 3, Clerus quadriguttatus Oliv. 

 (PL XXVI, fig. 3) June 15, and Cymatodera balteata Lee, July and 

 August 17. Hopkins ('93b, p. 187) reports that Chariessa pilosa 

 (PI. XXVI, fig. 6) is found under bark of walnut, and was taken 

 in a dead grape-vine, and reports also that it is predaceous. Felt 

 ('06, p. 504) figures this species and reports it on trees infested 

 with borers. 



The locust borer, Cyllene rohinim Forst. (PL XXVII, figs, i and 

 2), is a common insect in many localities, and the beetle is frequently 

 taken upon Solidago in the fall. The beetle was taken at Blooming- 



