148 



there October 15. The larvae of Neoclytus erythrocephalus Fabr. 

 (PI. XXVIII, fig. 4) are associated in dead elms with Magdalis 

 (Packard, '90, p. 228; Felt, '05, p. 70), and appear to follow injury 

 by Saperda tridentata. In hickory, Neoclytus has been found as- 

 sociated with Xylotrechus colonus Fabr., Chrysobothris femorata 

 Fahr., Catogenus rufus Fabr., and Tremex and Thalessa (Felt, 05, 

 p. 261). The cucujid Catogenus rufus was taken at Springfield July 

 20 by A. B. Wolcott. Liopus variegatus Hald., taken at Blooming- 

 ton June 1 1 and July 22, is reported under the bark and from several 

 kinds of trees. The cerambycid Smodicum cucujiforme Say is also 

 reported from under bark, and was taken July 6 at Bloomington. 

 Calloides nohilis Say, reported from oak stumps and hickory, was 

 taken at Chicago in June. From oak also Purpuricenus humeralis 

 Fabr. is reported. This was taken at Chicago, and June 9 at Bloom- 

 ington. The rare lymexylid, Lymexylon sericeum Harr., "a borer 

 in old oak wood," was talcen at Bloomington July 2. The larva of 

 the flat-headed borer Dicerca divaricata Say bores in the dead and 

 rotten wood of maple, cherry, etc. The beetles were taken May 9 

 and June 3 at Bloomington. Other wood borers whose records for 

 Bloomington should be given, are as follows : Leptura proxima Say, 

 a maple borer, June 1 3 ; Dorcaschema zvildii Uhler, an Osage-orange 

 and mulberry borer, June 19; Criocephalus obsoletus Rand, July 14; 

 and Oberea tripunctata Swed., whose larvae breed in twigs of cotton- 

 wood and blackberry, June 13 (Blatchley, '10, p. 1092). 



6. The Decaying Wood Community 



Thoroughly dry wood, or that submerged in water and thus shut 

 away from the air, remains sound for an indefinite period. In the 

 decay of wood, a certain amount of moisture, air, a favorable tem- 

 perature, fungi, and insects, are the main agents and conditions. 

 The fungi growing on wood remove the starch, sugar, and other 

 food materials, or they may dissolve the wood itself. This process 

 of course changes the character of the wood so that animals able to 

 derive sustenance from the solid wood now find it unsuitable for 

 their purpose; and still other kinds, on the other hand, unable to 

 eat the solid wood, are now able to feed upon the softened product. 



The rate of decay of trees varies greatly. The yellow locust {Ro- 

 binia) red cedar (Juniperus) , mulberry (Morus), and hardy catalpa 

 (Catalpa) are very resistant. This catalpa is reported by von Schrenk 

 ('02, p. 50) to serve as a railway tie for eighteen years and remain 

 sound ; as fence posts it has served from twenty-three to thirty-eight 

 years. Large stumps of white oak and walnut are also very durable. 



