
Other Invertebrates 
A principal means of studying populations of various small 
invertebrates was a method here designated as soil-surface sampling. The 
equipment used consisted of a foot-square frame with sides 6 inches high 
and a flanged top. This was placed on the ground and forced firmly into 
the sod an inch or so to prevent organisms from escaping or entering under- 
neath. Within the frame, the grass was cut to permit greater observation 
of the soil surface and facilitate capture of organisms. These were picked 
up with forceps and preserved for future analysis. Note was made of all 
organisms which eluded capture. Soil-surface samplings were taken at an 
average of 7 stations in all sprayed areas, as well as in the check area 
prior to the initial spraying, and were repeated once or several times 
after each treatment. Uniformity of topography, drainage, and vegetational 
cover were considered in selection of sites for the original samples. 
Succeeding samples were taken a short distance away, usually within several 
feet cf the first samples. 
In addition to soil-surface sampling, general observations and, 
in some instances, net sweepings were helpful in appraising population 
changes among small invertebrates. 
Spiders 
Despite subjection to periodic flooding by the tides, spiders 
are common inhabitants of the salt marshes. They serve in the role of 
predators upon insects and other small invertebrates and in turn are a 
source of food for larger organisms. Two of the most common and most con=- 
spicuous spiders included the wolf spider which builds no web but pursues 
its prey and the orb weaver which constructs a web. Investigations on the 
response of spiders to DDT applications were made by (1) general observa- 
tions, (2) marking of web locations, (3) soil-surface samplings, and () 
net sweepings. 
General observations revealed dead or dying individuals of the 
wolf spider within 2) hours after both sprayings in all areas, but partic-~ 
ularly in the two of higher dosages. Most of those observed were on the 
suriace of ponds or mud flats where they had strayed while affected by DDI. 
i few orb weavers likewise were noted dead in their webs on the day after 
spraying. 
Before the second spraying, active webs located in conspicuous 
sites were marked in the check area and in previously unsprayed portions 
of the 1.6 and 0.8 areas. These were observed for several days prior to 
treatment. On the fourth day after spraying no live occupants were noted 
in the sprayed areas while many of the webs in the check area were still 
in use. 
Soil-surface samplings before and after spraying revealed reduc- 
tions in the number of groung-inhabiting spiders in all areas following 
treatment. These decreases ranged generally between 50-90% and were greatest 
in the areas of high dosage. At the same time, sampling in the check area 
20 
