366 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 14 



INJURY TO STRUCTURAL TIMBER BY LEPIDOPTEROUS 



LARVAE 



By Thos. E. Snyder, Bureau of Entomology, U. S. Depa: Iment oj Agriculture 



Recently, Mr. T. D. J. Fuller, an architect of Washington, D. C, 

 called Mr. C. L. Marlatt's attention to the injury done by "fleshy 

 worms" to cypress pilasters of a beautiful new residence being built 

 on the forested bank of the Potomac River about one mile north of 

 Chain Bridge. At the request of Mr. Marlatt, I made an examiination 

 of the building on October 15, 1920, anticipating that the damage 

 would probably be due to either Bostrichid or "ambrosia" beetles. 



A superficial examination of the damaged pilasters, which had been 

 well painted with a white lead paint previous to attack by insects, con- 

 firmed this preconceived diagnosis. Small circular holes about | inch 

 ir diameter were found penetrating the wood not only of the pilasters 

 but were also in cypress columnar (hollow) pillars, window sills, frames 

 and other woodwork, all of which had been painted. The holes were 

 especially numerous at cracks and points of juncture, such as the mold- 

 ing of the pilasters, etc., which is normally the case in Bostrichid dam- 

 age, the insects being enabled to obtain a purchase or support by means 

 of which the wood is more easily penetrated. The wood at such places 

 looked as if it had been "riddled" with BB shot. In quite a few 

 instances, especially where the insects had attempted to enter the 

 wood at a distance from cracks or joints, the holes were incompleted, 

 i.e., only slightly penetrated the wood. 



What was my surprise upon inserting forceps into one of the com- 

 pleted holes to pull forth a wriggling Lepidopterous larva with "sor- 

 did white" ^ body and brown head, about one inch long. Further ex 

 amination showed that the larval burrows branched at right angles to 

 the entrance holes and extended longitudinally with the grain A the 

 soft cypress wood either up or down the pilaster. The burrows were 

 only slightly wider than the larvae. Sometimes frass protruded from 

 the entrance holes, being loosely held together by webbing. 



These larvae were submitted to Mr. Carl Heinrich for determina 

 tion and proved to be the Polygontim feeder (Pyrausta ainsliei Hein- 

 rich), a native American species of the family Pyralidae closely related 

 to the notorious European com borer (P. nuhilalis Hiibner). Pains- 



