144 



roots in such a manner as to hold the turpentine flowing into it. Thus 

 the larvae are often completely submerged in the viscid substance, 

 which does not appear to interfere with their progress." There are 

 thus marked differences in these beetles in their response to sap. As 

 a result of utilization of the knowledge of this difference, the larvae 

 sensitive to an excess of sap may be killed in trees by diverting a large 

 amount of it into the infested bark. This plan was proposed and 

 practised by Robert on conifers as quoted by Packard ('90, pp. 29- 

 30) ; and by Hopkins ('99, p. 391) for the elm. By "cutting narrow 

 strips of bark from the trunks of infested elms, the Scolytids were 

 either killed or driven out by the increased vigor of the tree and the 

 greater flow of sap which it is well known will result from this treat- 

 ment." 



The trunk of a tree is of such a substantial nature that it can not 

 be destroyed at once by animals. Such durability furnishes an oppor- 

 tunity to see how one kind of insect prepares the way for attack by 

 others, as is shown by the following examples. The elm borer, Sa- 

 perda tridentata Oliv. (PI. XXIV, figs. 3 and 4), invades weakened 

 trees, and it is followed (Felt, '05, p. 70) by the weevils Magdalis 

 armicollis Say (PI. XXV, figs. 1 and 2) and M. barbita Say, Neo- 

 clytus erythrocephahis Fabr., and, as a parasite of Saperda, Melano- 

 bracon simplex Cress., and Bracon agrili Ashm., which is a parasite 

 of Neoclytus (1. c, p. 73). Four other insects have been found as- 

 sociated with Magdalis barbita (1. c, p. 74). Xylotrcchns colonus 

 Fabr. (PI. XXVIII, fig. 6) appears to be able to kill hickory, and 

 from such wood many insects have been reared by Felt ('05, p. 261). 

 Felt and Joutel ('04, p. 18) state that in hickories dying from injury 

 by Scolytus quadrispinosus Say (PI. XXV, fig. 3) the beetle Saperda 

 discoidea Fabr. follows, living under the bark. 



The absence of woodland Ceranibycidcc, Scolytidce, and Bupresti- 

 dce in the Charleston collections eliminates the most important and 

 largest variety of insect inhabitants of tree trunks.* In addition to 

 the beetles which invade trunks, the large boring caterpillar, Prio- 

 noxystus robinics (cf. Packard '90, p. 53), and the horntail larva, 

 Tremex columba, are able to do much injury. The caterpillar can 



*I visited the Bates woods on June 8, 1914, and found a number of insects 

 in a recently cleared part of the upland area about a stump of a black oak (Q. 

 velutina). Running about in the sun on the top of the stump was Chrysobothris fem- 

 oral a Fabr., near the stump was a eerambycid, Stenosphenus notatus Oliv., and on 

 the bark, shaded by a vigorous growth of suckers, were the cockroach Ischnoptera 

 incequcMs Sauss.-Zehnt., the tenebrionid beetle Meracantha contract a Beanv., and the 

 otiorhynchid Pandeletejus hilaris Hbst. About the base of the stump was a large 

 funnel-shaped spider-web beneath which and in its meshes were remains of the fol- 

 lowing insects: Chion cincUis (eerambycid), Meracantha contra eta, Chrysobothris 

 femorata (several specimens), an Agrilus, Passalus comutus, and Lachnosterna. 



