Fortunately for man and his interests, the majority of insects 
are either innocuous or beneficial. The remainder, unfortunately, 
include some of his most important enemies—not only do they 
feed on him and other animals and often transmit deadly or debil- 
itating disease organisms, but they also devour his crops and 
decimate his forests. Because of their abundance, their fantastic 
reproductive powers, and their remarkable capacities for adapting 
to changing conditions, they present a continuing challenge to 
man in his efforts to limit their numbers to tolerable levels. 
Several general references to insects are available for consulta- 
tion: Leonard (454), Brimley (101), Essig (232), Comstock 
(152), Imms (391), Matheson (510), Brues, Melander and Car- 
penter (114), Ross (624), and Borror and DeLong (90). 
Class CRUSTACEA 
Wood Lice 
Crustaceans are aquatic organisms, mostly marine. They occur 
throughout the world, and several species attack the wood of most 
species of trees when they are placed in salt water. The surface 
of heavily infested wood may be so completely honey-combed that 
it resembles a sponge. When this damaged wood is removed by 
wave action, deeper layers of uninfested wood are exposed. They, 
in turn, are attacked and the process of destruction is repeated. 
Continuous infestation may result in the loss of the outer 1 inch 
of wood per year, Infested pilings often have an hour-glass shape 
as a result of the erosion of infested portions between low- and 
high-tide marks. Heaviest attacks occur between mean tide level 
and low tide, but serious damage sometimes occurs at water depths 
of 40 to 70 feet or more (9). 
Limnoria ignorum (Rathke), commonly called the wood louse, 
is one of the most destructive species. It has seven pairs of legs, 
sharp claws for holding onto the wood, and a pair of toothed 
mandibles for boring into it. Full-grown specimens are 3 to 6 mm. 
long and resemble sowbugs. This species occurs in clear salt water 
only and spreads slowly, usually in infested driftwood. 
Members of the genus Sphaeroma are beetle-like in appearance 
and are up to 12 mm. long. They occur in both salt and fresh 
water and may be found in such places as crevices, empty barnacle 
Shells, and in burrows made by molluscan borers. They also dam- 
age pilings, usually between tide marks but sometimes all the way 
down to the mud line. Damage is usually less severe than that 
caused by Limnoria, however, even though the burrows are some- 
what wider and penetrate to depths of 3 or 4 inches. 
The genus Chelura contains the largest of the wood-boring 
crustaceans. None of these initiate attacks on wood, but they do 
invade and enlarge burrows made by shipworms. C. terebrans is a 
well-known species along the Atlantic Coast. 
Methods for protecting timbers from wood-boring crustaceans 
are the same as those used against molluscan borers. 
