




eFF ECTS OF SPRAYING ON INVERTEBRATES 
Insects 
The New Jersey Agricultural Experiment Station conducted insect 
mortality studies in connection with the first spray treatment and made 
special investigations on the effects upon mosquito larvae and pupae and 
upon greenhead flies. The results of this work are reported elsewhere. 
Kinds 
Nine orders of insects were represented inthe sweepings and 
collections made on the salt marsh in September and October. Of these 
orders, only two, leafhoppers (Homoptera) and flies (Diptera), were abundant. 
Fairly common insects included true bugs (Hemiptera) and the wasp group 
(Hymenoptera). The grasshopper group (Orthoptera), lace-wing group 
(Neuroptera), beetles (Coleoptera), and butterflies and moths (Lepidoptera) 
ware the other orders found in sweepings. Dragonflies (Odonata) were also 
present but were absent from the sweepings due to their-swiftness of flight. 
Methods of Study 
Net sweepings were made before and after sprayings to determine 
DDT spraying effects upon the insect fauna ofthe salt marsh. Sweepings 
were accomplished with a standard insect collecting net 15 inches in 
diameter, 100 sweeps comprising a sample. Courses.about 160 feet long, 
well away from the area boundaries, were marked off in all spray areas 
and in the check area. Two or more were placed in uniform portions of the 
tallegrass and short-grass habitats of an area. All subsequent sweepings 
were made along the same course or a short distance to one side where 
possible. 
Net Sweepings 
Sampling in the check area before the second spraying showed an 
average of 80) insects per 100 sweeps in the short grass and 576 in the 
tall grass. These preliminary samplings also indicated that the check area 
was not fully comparable to untreated portions of the 1.6 and 0.8 areas, 
the test plcts having populations 1/3 to 2/3 less on the average than the 
check. For this reason most of the comparisons made in the following dis- 
cussion are based on pre= and post-spray figures obtained within the same 
area. 
Effects of first spraying.--Early September insect sweepings of 
the 1.6 and 0.8 areas revealed the following population decreases in sprayed 
portions when compared to unsprayed portions: 
1.6 area: 80% decrease in short grass 
42% decrease in tall grass 
0.8 area: 59% decrease in short grass 
21% decrease in tall grass 
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