

10 
400 times that in soil, but declined thereafter with small, 
nonsignificant fluctuations corresponding to the seasonal 
pattern in earthworms. Total DDT metabolites in earth- 
worms averaged 47 times that in soils 2 months after appli- 
cation; ratios fluctuated thereafter, generally following 
the seasonal pattern. Fluctuations of the ratios with dif- 
ferent sampling periods probably explain the lack of 
significant correlations between soil and earthworm resi- 
dues for the 2-year period. 
Total DDT and metabolites in soils and earthworms 
were compared by stepwise regression with the other fac- 
tors measured in this study (Table 6). Percent organic 
matter and amount of rain during the 2 weeks before sam- 
pling influenced soil residues of total DDT compounds, 
but their influence was not significant. Other factors had 
no measurable influence on soil residues. However, the 
other factors were responsible for some of the variability of 
earthworm residues. Nearly 74.5% (P < 0.01) of the var- 
iability of total DDT residues could be accounted for by 
the equation 
Y = -—2.47967 + 0.79089 X, — 0.04027 X, 
+ 0.04837 X, + 0.37466 X, 
where Y is the predicted logarithm of ppm in earthworms, 
X, is the logarithm of ppm in soils, X, is months after treat- 
ment, X, is the percent moisture in earthworms, and X, is 
the percent lipid in earthworms. This equation is merely 
descriptive, and its limitations have not been determined. 
It may prove useful for predicting quantities of total DDT 
and metabolites in earthworms. 
The occurrence of gradually increasing quantities of 
p,p'-DDE in soils over the 2 years is consistent with labo- 
ratory studies of aerobic soils. The DDT was biodegraded 
to DDD under anaerobic conditions (Guenzi and Beard 
1967, 1968) and disappeared much faster in submerged 
soil than in aerobic soil (Ko and Lockwood 1968). The 
main metabolite of DDT in soils under anaerobic condi- 
tions was DDD, whereas DDE was the most abundant 
metabolite under aerobic conditions (Guenzi and Beard 
1968), We detected a relatively small, nonsignificant 
reduction in p,p'-DDT, whereas p,p'-DDE, not present in 
the wettable powder, increased significantly from trace 
amounts at the onset to levels approaching 1 ppm. The 
o,p'-DDT component did not change significantly from 
the first sampling period and may be relatively less imper- 
vious to degradation by microorganisms than p,p’-DDT. 
Both o,p'-DDT and p,p'-DDT were highly persistent in 
soils, confirming the observations by Dimond et al. (1970). 
The pathway for metabolism of p,p'-DDT in earth- 
worms is more complicated because worms accumulate 
residues which have been partially subjected to degrada- 
tion by soil microorganisms. There is considerable evi- 
dence that the microflora of the mammalian gastrointesti- 
nal tract can dechlorinate p,p'-DDT to p,p’-DDD 
(Braunberg and Beck 1968; McCulley et al. 1968). 
Whether or not earthworms contain similar microflora, 
they ingest soil which contains organisms capable of de- 
chlorinating DDT to DDD under anaerobic conditions 
(Guenzi and Beard 1967, 1968). Based on the large quanti- 
ties of p,p'-DDD in earthworms in our study, it appears 
that DDT is dechlorinated to DDD in earthworms, Pre- 
sumably the DDD is further dechlorinated to DDE, 
although Davis (1971) was unable to detect this conver- 
sion. He also suggested that p,p'-DDT goes directly to 
p,p'-DDE in earthworms (Davis and French 1969; Davis 
1971). The two hypotheses are not necessarily mutually 
exclusive and may reflect the different conditions of each 
study. The o,p'-DDT component in soils was not found in 
earthworms in the present study; o,p'-DDT has been 
reported in earthworms by others (Collett and Harrison 
1968; Davis 1968; Wheatley and Hardman 1968; Davis 
and French 1969; Bailey et al. 1970; Gish 1970) but not in 
all samples. Davis (1971) has shown that both 0,p'-DDT 
and p,p'-DDE appear in A. caliginosa after 15 days in 
o,p'-DDT treated soils. 
Environmental levels of DDT resulting from a program 
to control Dutch elm disease were followed for about 15 
months after the last application (Boykins 1964, 1966). We 
selected data from Boykins’ study (1964) for time trend 
comparisons by using only the study areas that had soil 
and earthworm samples from every period. Our statistical 
analysis of his data showed that residues of DDD + DDT 
declined linearly with time (P < 0.01) in both soils and 
earthworms, whereas our soil residues did not change. In 
contrast to our study, seasonal fluctuations of DDD + 
DDT in earthworms were not evident, but such an effect 
would not have been obvious in only 15 months (see Table 
3). Because Boykins (1964), using the Schecter-Haller ana- 
lytical method (Schecter et al. 1945), quantitatively deter- 
mined DDT at 600, DDD and unknown amounts of 
other substances were included in the measurement but 
not DDE, which is read at 540y. This fact may partially 
account for the rapid decline in his estimates of total 
DDT. Dimond et al. (1970) found higher amounts of total 
DDT and metabolites in earthworms from forest soils re- 
ceiving more frequent DDT application; however, no 
time trends were obvious. Ratios of residues in earth- 
worms to residues in soils were less than 1.0, a situation 
that occurred only with p,p'-DDT in our study. In two 
studies, residues of DDT and metabolites in soils and 
earthworms were followed for 12 (Collett and Harrison 
1968) and 15 (Bailey et al. 1970) months. Soil residues 
varied with the spraying program in the 15-month study 
(Bailey et al. 1970) but did not change in the 12-month 
study (Collett and Harrison 1968). Fluctuations in earth- 
worm residues in both studies appeared to follow the spray 
program; no seasonal fluctuations could be determined 
from the sampling periods used in either study (Collett and 
Harrison 1968; Bailey et al. 1970). 
Heptachlor Plots 
Two subsamples of wettable powder formulation with 
“95%” technical heptachlor averaged 28.5% active 
