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Determination of the spatial pattern and estimation of the density of egg, larval, and adult populations of Ctenicera destructor (Brown) and Hypolithus bicolor Eschscholtz were made by soil sampling, and for C. destructor adults, also by cages that collected the emerging adults in the spring. Eggs of both the above species and also those of Aeolus mellillus (Say), which were also found in the samples, were highly aggregated. Small C. destructor larvae were most highly aggregated and medium larvae less so; large larvae were usually randomly distributed. Unlike C. destructor, large H. bicolor larvae were more highly aggregated than either the small or medium bicolor larvae. Sampling by emergence cages showed that C. destructor adults were aggregated while sampling by soil cores showed them to be randomly distributed. The different result obtained by the two methods was attributed to the difference in the size of the sampling unit. Aggregation was detected in 29% of the H. bicolor adult population sampled by soil cores only.
Larval densities of C. destructor ranged from a low of 0.25 to a high of 1.46 per sample unit (81 cm2) over the 14-year period that samples were taken; densities of H. bicolor ranged from 0.16 to 0.64. Densities of C. destructor and H. bicolor adults averaged about 6 (range 1–16) % and 12 (0–27) % of the total population of larvae and adults for each respective species. Population composition, in terms of adults and larvae of different sizes, and population fluctuations are discussed.
The relation between density and the number of sampling units required to achieve four levels of margin of error at four levels of statistical significance was determined.
No satisfactory transformation was found for data of individual samples with a mean less than 1. Several common transformations, including Taylor’s power transformation, were satisfactory for stabilizing the variance of pooled samples.
