INSECT ENEMIES OF EASTERN FORESTS OI 
The Ambrosia Beetles 
The ambrosia beetles are not a compact group distinguished by 
anatomical differences from the true bark beetles. Although simi- 
larities in the structure of certain organs set most of them apart from 
bark-eating forms, these differences have apparently been brought 
about as adaptations, associated with their different mode of life and 
different food habits. Their true taxonomic affinities to various groups 
of bark-eating forms are plainly indicated by the structural similari- 
ties of such body parts as would not be greatly affected by peculiarities 
in their habits. The mode of life of the ambrosia beetles has been 
discussed in the general portion dealing with the entire group (pp. 
294-299) and needs only to be briefly summarized here. The burrows 
extend directly through the bark into the sapwood and are there 
elaborated into simple, branched, or compound ambrosial burrows, de- 
pending on the species. Not all the species of each genus of ambrosia 
beetles necessarily construct the same type of burrows. The fact is 
illustrated by the work of Yyleborus, where ambrosial burrows of all 
three general types are made by different species of the group. 
The food of both larvae and adults consists of the tender shoots of 
ambrosial fungi grown on the walls of the galleries. In both the 
simple and branched galleries the larvae move about freely in at least a 
portion of the burrow and feed on these fungi directly. In the com- 
pound type of burrow each larva has its own special niche, branching 
from the main gallery, in which it spends its entire larval, pupal, and 
callow adult stages. It is here tended by the adults, who supply each 
larva with ambrosial food and remove the debris. Most of the am- 
brosia beetles breed in decadent or recently cut trees, often entering 
the wood of otherwise healthy trees through some injured or dying 
area of the bark. Since they require considerable moisture, seasoned 
wood is not suitable. In the tropics, especially, a few species will 
enter the wood of casks containing water, wine, or other hquids, 
causing leakage and loss. A few species breed in living trees, with 
apparently little effect on their health. 
The chief damage by ambrosia beetles is due to the black-stained 
galleries made by them in the sapwood of trees felled for lumber. 
Timber cut during the time the beetles are active will almost invariably 
suffer injury unless utilized at once. This is especially true in the 
Southern States, and there lumbermen know from experience that it 
is a good practice to saw up their cypress, oak, gum, and other logs, 
felled during the warmer months, within 2 weeks. Even within that 
period, the timber will usually have been attacked, but if sawed 
promptly all or most of the injury will be removed in the slabs and 
edgings. 
Aside from prompt sawing, other methods of preventing excessive 
injury to logs felled in the warmer months, are rapid seasoning of such 
material, storage in water, or removal of the bark. Rapid seasoning 
can be accomplished in some areas and some seasons by placing the 
logs in full sunlight, and free of the ground. Turning the logs after 
about 2 weeks will aid in drying out the under side and will often kill 
any beetles that have entered. Storage in water will render the wood 
too moist to be attractive to ambrosia beetles and will cause a gradual 
