showed the number of spiders there to be greater than when the original 
pre-spray samples were taken. Portions of the 1.6 and 0.8 areas treated 
only in august showed little or no recovery of populations by the end of 
September. 
Net sweepings gave information or. the effects of the second 
spraying on web builders and other species of spiders inhabiting the strata 
above the soil surface. Decreases in population after spraying were noted 
in almost all cases and, as indicated by the soil-surface samplings, the 
greater decreases were observed at the higher dosage rates. However, the 
populations in the check area also showed a decrease. In early September, 
populations on unsprayed portions of the 1.6 and 0.8 areas were about 2.5 
to 3 times as great as populations on sprayed portions. 
Red Mites 
Red mites are common on the soil surface and vegetation of the 
salt marsh. Contrasted to the decline in spider populations after spraying, 
there was a general increase in numbers of red mites as revealed by soil- 
surface samples. A comparable population rise also occurred in the check 
area, possibly due to a seasonal increase. The largest increases occurred 
after the second spraying in the area of highest dosage. Similar indica- 
tions were obtained from net sweepings. These increases in red mite popu- 
lations following DDI spraying appear to correspond to those observed by 
other investigators elsewhere. 
Marsh Flea, Orchestia grillus 
The marsh flea is an amphipod and a close relative of the better- 
known beach flea (0. platensis). It occurs on or beneath the soil surface, 
being most common in protected places at or above the high-tide zone. 
Fish, birds, and other vertebrates feed upon it, and it also has value as 
a scavenger. 
Soil-surface sampling proved ineffective in measuring populations 
of these elusive organisms. Nevertheless, the effects of DDT spray appeared 
clear-cut. Though an average of two individual marsh fleas (highest single 
count 16) were seen in foot-square samples prior to the first spraying, no 
live ones were found by this method on any of the areas after treatment. 
This held true for 11 weeks, the period during which observations were 
made. At the same time, original numbers were maintained or increased on 
the check area, 
Saltmarsh Sowbug » Philoscia sp. 
As in the case of marsh fleas, saltmarsh sowbugs were found to 
be too elusive to count readily by the soil-surface sampling method. In 
general they were common, an average of 1.6 individuals (highest single. 
count 49) being found in a foot-square area prior to spraying. General 
observations showed that DDT was very destructive to these isopods. Live 
sowbugs were noted in only. two instances after an area had been treated: 
one individual in the 0.8 area 2) days after spraying and two in the 0.2 
val 
