Effects of Hyperparasites on Population Levels of Bathyplectes curculionis1 in Colorado 2

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Abstract
Cocoons of Bathyplectes curculionis (Thomson) often harbor hyperparasites. Emergence of all hyperparasites from diapause cocoons over a 5-yr period averaged 52.9%. Hyperparasites averaged 36% of the total emergence from diapause cocoons in 1969, increased to 74.1% in 1971%72, then dropped to the low of 29% in 1973–74. Emergence of all hyperparasites from nondiapause cocoons over a 3-yr period averaged 50.3%. Hyperparasites averaged 68.7% of the total emergence from nondiapause cocoons in 1970, then steadily decreased to the low of 36.3% during the last year. Populations of hyperparasites fluctuate from year to year which probably reflects environmental pressure. Most hyperparasites emerge from one type of cocoon (diapause or non-diapause) more than the other. The degree of hyperparasitism to larvae in either type of cocoon appears primarily dependent upon the predominance of one cocoon type (or formation of) over the other when hyperparasites emerge in the field. B. curculionis larvae in diapause cocoons are heavily hyperparasitized by S. grandiclava (Walker) and Mesochorus nigripes Ratzeburg, whereas those in nondiapause cocoons are heavily hyperparasitized by Mesochorus agilis Cresson and Eupteromalus americanus Gahan. The more important species have one or more favorable biological characteristics of multivoltinism, lack of diapause, extended longevity, or gregariousness.