THE SPIDER POPULATION 

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IV. THE SPIDER POPULATION. 

The earliest census recording the spider population of a stated area 

was that made by McAtee (1907) near Washington, U.S.A. His 

investigation was confined to 4 sq. ft. of ground in woodland and in 

meadow. The density of the spider population was equivalent to 

11,000 per acre of woodland and 64,000 per acre of meadow.* 

In 1922 H. M. Morris's census of arable land at Rothamsted, which 

was bare of vegetation except for a few weeds, yielded a spider 

density of 20,000 to the acre. Of these, 75% were Linyphiids. 

A recent investigation of grass plots at Rothamsted by W. Ladell 

and K. D. Baweja yielded a density of 159,000 spiders per acre 

in the 

soil 

after clipping away the grass to soil level. The results of this 

investigation are contained in a thesis written by Baweja in 1937 for 

his Ph.D. I have to thank the authorities at Rothamsted for permission 

to see this document and Ladell for exact figures of the spider 

captures. In contrast to Morris, whose sifting of the soil population 

was done by hand, Ladell and Baweja employed a flotation process 

for the separation of the invertebrates from the soil. 

The density of the spider population of a clay meadow near Oxford 

which had been untouched for three years was found by J. Ford (1935)

to be approximately 407,000. Like Ladell and Baweja he employed a 

flotation process, but in contrast to them, he did not remove the 

vegetation before counting the inhabitants. His results agreed with 

those at Rothamsted and in Central Europe (Frenzel) in that the total 

invertebrate population is higher in the 

*McAtee's figures were 11 and 53 spiders respectively. The former, however, is shown to 

include a mite and a pseudoscorpion, so this must be reduced to 9. The meadow census is not 

analysed, so it is probable that this figure also contains Arachnids other than spiders.