Many of the papers were reviewed a second time to make sure 
that the name of the species, was given if the author provided it and to 
standardize the expression of rates of application so far as possible. 
Authors varied widely in their practices, some testing worms in 
standardized solutions, others judging results from signs of earthworm 
work in the field. Some did not tell what the formulation or the rate 
of application was. Others did not name the species [at least 17 native 
species and 13 introduced species of earthworms occur in the area east 
of the Mississippi and north of Virginia (Eaton 1942)]. 
The worm most usually and most easily grown and hence most 
often used in experiments is the red worm or manure worm, Eisenia 
foetida, which appears to be extremely resistant to chemicals. The 
red worm is a creature of moist, highly organic sites where chemical 
concentrations are high. Most common worms of field and garden could 
not survive such conditions. Hence, use of the red worm in experiments 
is quite unwise if the results are to be applied to other earthworms. 
The general conclusion to which we wish to direct attention 
is that earthworms are indeed resistant to most chemicals, even at 
levels considerably higher than those used to protect crops from insects. 
It is extremely probable that, throughout the portions of the world 
that are treated with residual pesticides, earthworms are carrying 
burdens of toxicants. Some must be carrying several toxicants. 
If this is true, why have wildlife effects not been reported 
more commonly? Perhaps because they have so seldom been sought, perhaps 
because they occur so long after the application that they are ascribed 
to other causes. They may be spread over such an extended period that 
they are not observed. There are, however, several factors that serve 
to reduce the danger. Some chemical applications are not great enough 
to produce severely contaminated worms. Some soils hold the chemicals 
poorly. Earthworms are scarce in some soils, abundant in few. They 
are available in numbers to predators only at certain times. Most 
predators tend to spread their hunting over large areas; thus they are 
likely to feed on untreated areas part of the time unless large blocks 
are treated. And the predators are likely to feed partly on organisms 
less contaminated than earthworms, for few kinds of animals feed primarily 
on earthworms. 
The problem does not end with earthworms, however. Snails and 
other mollusks are resistant to pesticides and some contain large residues 
They are important wildlife foods. Other invertebrates, aside from 
insects, have hardly been studied in this connection. Insects them- 
selves must carry significant residues whenever contamination of the 
environment is within their tolerance limits. Clearly the problem is 
a pervasive one of which little is yet known. It seems safe to say, 
however, that the severity of the problem is bound to vary directly 
with the use of residual pesticides. 
- William H. Stickel 
