494 The American Naturalist. [June, 



ferent fungus for the different species of these beetles, even where several 

 species occur in the same tree trunk. The ambrosia of X. pubescens 

 and X. /meatus is deep black in its stain, or in its later stages, and the 

 same fungus may serve both these species ; but X. xylographus, a cos- 

 mopolitan species frequently found in hickory, oak, beech and the like, 

 has a very different ambrosia, which is olive-green when dry, or leaves 

 a 3tain of that color in the chambers. The ambrosia of X. celsus, a 

 large species found in hickory, is dark brown in stain and in the form 

 of its conidia is entirely different from that grown by any other of the 

 species I have mentioned. 



In the orange trees injured or killed by frost the most numerous 

 borer is Platypus compositus. Its ambrosia is entirely different from 

 that of the Xylebori in the orange, and stains the chambers dark 

 brown. Several species of Platypus are found in the Southern States 

 in all sorts of timber, conifers and deciduous trees alike, P. compositus 

 attacks all sorts of trees, including our pines. 



The scolytid boring into the whortleberry, which I brought to the 

 Department of Agriculture last fall is Corthylus punctatissimus. It 

 lives in the roots of several shrubs, as hazel, witch hazel, etc. Its 

 ambrosia leaves a deep black stain. Corthylus columhianus, discovered 

 by Hopkins, makes notable black stains in Liriodendron wood. 



I have had the opportunity of examining three or four kinds of am- 

 brosia and have found them very distinct in the form and arrangement 

 of the conidia as well as in the habit of growth of the mycelium. There 

 is, I think, very little doubt that the different species of ambrosia are 

 connected with certain scolytid beetles irrespective of the wood in 

 which they make their galleries. The different genera in which I have 

 found the food to consist of ambrosia are Platypus, Xyleborus, Mon- 

 arthrum and Corthylus. It is useless to give lists of plants attacked 

 by these ambrosia-raising beetles because most of them make their gal- 

 leries and brood chambers in a great variety of trees and shrubs 

 Some species live preferably in the roots of plants and others in the 

 trunks or larger branches, but very few species are restricted to one or 

 even a few kinds of timber. 



I expected to learn much about the forms of ambrosia found in gal- 

 leries of the different borers in orange trees, but I find on my return 

 here this winter that a f' i mon of all the 



ambrosia which I have examined, and the operations of the beetles are 

 for the time being at a standstill. A slide of the material now lining 

 the galleries [Feb. 20, 1896] shows only fragments of the mycelium of 

 the fungus, and the entire field swarms with bodies like yeast (or bac- 



