X. germanus reproduced in debarked sections from green elm trees that were placed upright on wet sand in 3-gallon battery jars which were covered with muslin and glass. They attacked but did not reproduce in similar sections from which the bark had not been removed. Sections with bark taken from trees injected with 100-300 cc. of 50% ethyl alcohol per diam.-inch proved more suitable for beetle reproduction than debarked sections from trees that had not been injd. with alcohol. In the field beetles bored into but did not reproduce in areas on trees from which the outer bark had been shaved thin or removed, but did not bore through uninjured bark of normal trees. However, X. germanus readily bored through uninjured bark and reproduced in field trees that had been injd. with ethyl alcohol. No external symptoms of the Dutch elm disease developed in 90 field trees that were attacked by the beetles through areas on the trunk where the outer bark had been shaved off, nor was Ceratostomella ulmi isolated from 80 beetles or the wood tissue surrounding 178 entrance holes in 36 trees. The Dutch, elm disease, however, did develop in 13 trees that were attacked by X. germanus artificially contaminated with C. ulmi and confined to areas from which the outer bark had been shaved. Larvae removed from their brood chambers transformed to adults after feeding for over a month on one of the following fungi: Ceratostomella ulmi, C. pluriannulata, Pestalozzia sp., and one unidentified fungus.