24 



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1 



of logs. It lias been found in Ontario, Canada, in freshly cut maple 

 stumps. 



Xyleborus celsus Eiclih. (fig. 18, female aud male). — This is the largest 

 American species of the genus. It has been found only in hickory 

 trees. The galleries, shown in fig. 19, have a short entrance passage, from 



the end of which numer- 

 ous branches radiate in 

 a nearly horizontal plane. 

 They penetrate deeply into 

 the heartwood and greatly 

 promote decay in the tim- 

 ber. The galleries are 

 blackened as if by fire, but 

 the stain does not extend 

 deeply into the wood. 



The ambrosia, fig. 20, 

 consists of club-shaped 

 stems growing upright in 

 dense clusters. Thejoints 

 are long, and the terminal 

 conidia when they separ- 

 ate are several timeslonger 

 than wide. An umber- 

 brown discoloration tinges 

 the base of the clustered 

 stems, but their termina- 

 tions are pellucid and filled with colorless protoplasmic granules. 



The young and adults of the beetles live socially in the galleries and 

 the pupse are formed lying free in the 

 passages. 



The male of X. celsus was described 

 by LeConte under the name of X, 

 biogra/phus. 



. Xyleborus xylographus Say {=saxeseni 

 Eatz.) (fig. 21). — This is a slender elon- 

 gate species, which can be distinguished 

 from all others by the very regular rows 

 of small but sharp teeth upon the 

 declivity of the elytra. 



The young in this species are assem- 

 bled in a brood chamber, the usual form of which is represented in 

 fig. 22. It is constructed at the end of a gallery which penetrates 

 deeply into the heart, or remains in the sapwood, according to the 

 amount of moisture in the tree trunk. The chamber is somewhat leaf- 

 shaped, and stands vertically on edge, parallel with the grain of the 

 wood. The space between the walls is not much greater than the 



Fig. 20. 



-Ambrosia of Xyleborus celsus— greatly enlarged 

 (original). 



Fig. 21. — Xyleborus xylographus: Female 

 and male— enlarged (original). 



