Hypothenemus rotundicollis (Eichhoff) occurs in the Southeastern States and 
breeds in the limbs of oaks and hickories. The adult is dark brown to black and 
about 1.6 to 1.8 mm long. H. quercus (Hopkins) attacks various oaks, 
hophornbeam, honeylocust, and hickories in the Southeastern States. The adult is 
dark brown and from 1.5 to 1.9 mm long. H. chapuisi (Eichhoff) breeds in 
sassatras and redbud. It has been recorded from Texas, Mississippi, Georgia, and 
North Carolina. The adult is dark brown to black and about 1.9 mm long. H. 
interstitialis (Hopkins) attacks oaks, hickory, walnut, and many other hardwoods. 
It has been recorded from Connecticut and Kansas to Florida. The adult is dark 
brown to black and from 0.9 to 1.6 mm long. There is a slightly reddish rugose area 
on the pronotum. The adult is dark brown and from 1!.1 to 1.6 mm long. H. 
obscurus (F.) 1s frequently intercepted in shipments of Brazil nuts. H. eruditus 
Westwood attacks dogwood, redbud, hickory, and black cherry from Michigan and 
New Jersey south to Argentina. The adult is dark brown to black and from 1.1 to 
1.3 mm long. 
Ambrosia Beetles 
Xylomycetephagus Scolytidae 
Numerous species of beetles in the families Scolytidae and Platypodidae are 
known as ambrosia beetles because, in all cases, both the adults and larvae feed on a 
mold-type of fungus known as “‘ambrosia.”’ The beetles introduce this fungus into 
tunnels bored into the sapwood and sometimes heartwood of trees and logs, where 
it grows on the walls and is propagated. Female ambrosia beetles possess spe- 
cialized structures called mycetangia (479), which are variously located in and on 
the body of the insect. In a few species these organs are found in the male and, in at 
least one species, Xyloterinus politus (Say), 1n both sexes (2). Since the discovery 
that these specialized organs are possessed by ambrosia beetles, much important 
knowledge about the relationship of beetles to their specific microsymbiotic com- 
plexes has been gained (4/, 67, 392, 393, 441). 
More than 54 genera of ambrosia beetles, some of which include up to 1,200 
species, have been recorded throughout the world. A number of species breed in 
living trees, but decadent, dying, or recently cut trees, logs, and pulpwood or 
stumps are usually preferred. All species require a considerable amount of moisture 
for development. In the Southern States, timber is not attacked unless the moisture 
content of the wood is at least 48 percent. Seasoned timber is never infested (205). 
Ambrosia beetles are important chiefly because of the degrade of sawed lumber 
that results from their invasion of trees or logs. This degrade is caused both by holes 
bored into the wood and by the presence of black stains caused by the fungus 
inhabiting the tunnels. Trees cut during the summer in the South and left for more 
than 2 weeks in the woods are often severely damaged. This is especially true of 
sweetgum, baldcypress, and oak logs. 
There are four general types of ambrosia beetle tunnels: simple, branched, 
compound, and cave. Simple tunnels are unbranched, often penetrating deeply into 
the wood. Branched tunnels penetrate deeply into the wood and then break up into 
several branches that extend in various directions on the same plane. Compound 
tunnels also branch off from a single entrance gallery but have egg niches extending 
upward and downward from the tunnel. In the cave-type gallery, a simple tunnel 
extends into the wood where it is expanded vertically upward and downward into a 
cavelike chamber in which the eggs are laid. One of the most common is the cave- 
type cavity made by Xyleborinus saxeseni. As these tunnels are excavated, the 
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