INSECT ENEMIES OF EASTERN FORESTS 69 
The wood louse Limnoria has been considered the most destructive 
of the three forms mentioned above, but it has lately been reported 
that the associated form Chelura is assuming greater importance in 
some localities. 
Limnoria lignorum (Rathke), the most destructive species, is 
capable of reducing piling about 1 inch in diameter per year. It has 
seven pairs of legs, with sharp claws to hold onto wood and a pair 
of toothed mandibles with which to bore into the wood that serves 
as its food. Being poor swimmers, these animals spread slowly from 
a center of infestation, and are usually carried by infested driftwood. 
When mature, Lemnoria are from 1% to 14 inch long. They seldom 
penetrate more than 14 inch directly into the wood. Sometimes they 
make oblique galleries an inch or more long. | 
Sphaeroma, although slightly larger (up to 1% inch long) is less 
numerous and less destructive than Limnoria, although its burrow is 
relatively wider and penetrates to a depth of 3 to 4 inches. It isa 
southern species, and is sometimes found working in fresh water. 
CONTROL OF MARINE BORERS 
Although it is possible to control marine borers by the use of me- 
chanical barriers and paints, the standard pressure treatments of 
southern pine and Douglas-fir with coal-tar creosote, or creosote-coal- 
tar solution, have been found to be most practical. Such timbers, when 
thoroughly impregnated with dosages of at least 20 pounds per cubic 
foot, respectively, for Douglas-fir and southern yellow pine in ac- 
cordance with recommendations in Federal specifications (419) should 
give long service under average conditions, whereas untreated piling 
along the Atlantic and Gulf coasts may be destroyed within a year 
or less. 
THE FOREST INSECTS °” 
PRACTICAL KEYS TO THE ORDERS, FAMILIES, AND 
GENERA OF FOREST INSECTS, BASED ON TYPES OF 
INJURY 
The keys that follow are designed to aid those who are not familar 
enough with the orders of insects to recognize and place the insect 1m- 
mediately under the correct order, from which they may work down 
to a particular insect or specimen of injury.” In keys of this kind, it 1s 
° An effort has been made to refer to each insect, wherever possible, by a common 
name in general use by forest workers or woodsmen. These common names 
are printed in bold-faced type. Many little-known insects or species not easily 
distinguished from similar forms, except by entomologists, are designated by the 
scientific names alone. An approved name, as given in a list of approved Common 
names of insects, published by the American Association of Economie Entomol- 
ogists, is placed before the scientific name and the latter is set off by parentheses. 
Other names not so established, but used locally or perhaps generally, are placed 
after the respective scientific names and set off by commas, in accordance with 
the style used in Department of Agriculture publications. It is suggested in the 
interest of a definite nomenclature that the approved names be used regularly in 
preference to the various local names of insects. 
Tor those who are able to recognize the order to which an insect belongs 
the simplest procedure is to turn to the key preceding that order in a later section 
of this publication and seek its specific determination in that place. 
