Field and Laboratory Observations of Hexamermis arvalis (Nematoda: Mermithidae) a Parasite of Cutworms1

Abstract

In Missouri and adjacent States, the nematode Hexamermis arvalis Poinar & Gyrisco was commonly found in clover and alfalfa fields parasitizing the dingy cutworm, Feltia subgothica (Haworth), the black cutworm, Agratis ipsilon (Hufnagel), and the bristly cutworm, Lacinipolia renigera (Stephens) (Lepidoptera: Noctuidae). Other noctuid larvae occurring in the same habitat were never found parasitized, and young nematodes found in larvae of the clover leaf weevil, Hypera punctata (F.), always succumbed to encapsulation by blood cells of the host. H. arvalis proved to be univoltine. Infective juveniles parasitized overwintering 1st- and 2nd-stage lepidopterous larvae in the fall, completed their development, and emerged from 4th- and 5th-stage larvae in late spring of the following year, entered the soil, molted to adults in about 1–2 months, mated, and laid eggs that apparently aestivated. A method of rearing postparasitic juveniles to adults was devised, and a method of sampling field population of the nematode was successful. The nematode reared from the cutworms may be different from H. arvalis described from Hypera postica (Gyllenhal).