Class Crustacea— Wood Lice 
Crustaceans are primarily marine organisms. They occur throughout the world, 
and several species attack the wood of most species of trees when the wood is 
placed in saltwater. The surface of heavily infested wood may be so completely 
honeycombed that it resembles a sponge. When this damaged wood 1s 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 2 cm of wood per year. Infested pilings often have an 
hourglass 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 12 to 21 m or more (2/). In 
contrast, Oniscus asellus L., the common terrestrial sowbug, and related species 
are usually beneficial. In certain habitats they rapidly ingest decaying leaves and 
wood, releasing nutrients needed for plant growth. 
Limnoria lignorum (Rathke), the woed 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 saltwater only and spreads 
slowly, usually in infested driftwood. 
Members of the genus Sphaeroma are beetlelike 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 damage 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, even 
though the burrows are somewhat wider and penetrate to depths of 8 to 10 cm. 
The genus Chelura contains the largest of the wood-boring crustaceans. None of 
these initiates attacks on wood, but they do invade and enlarge burrows made by 
shipworms. C. terebrans Philippi 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. 
Class Diplopoda—Millipedes 
Millipedes are slow-moving, elongate, wormlike organisms, usually with 30 or 
more pairs of legs. Generally they are found under bark, stones, old boards, or in 
damp rubbish. Their food consists of decaying vegetable matter. The adult has two 
body regions: (1) the head, which bears a pair of short antennae, usually seven- 
segmented; and (2) the rest of the body, which consists of a large number of similar 
cylindrical segments. The first four or five body segments are not fused, and each 
bears a single pair of legs. The remaining segments are fused into ringlike joints, 
each of which bears two pairs of legs. Narceus americanus (Beauvois), one of the 
larger species, is dark brown, narrowly ringed with red, and about 10 cm long. 
Millipedes sometimes become abundant. At such times they may invade camps, 
old buildings, and residences in large numbers. Many species emit a fluid with a 
cyanidelike odor through openings along the sides of the body. Removal of moisture 
and of accumulations of vegetable matter from infested areas should be helpful in 
control of millipedes. Discussion of numerous species occurring in the Eastern 
United States may be found elsewhere (/3/2). 
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