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Introduction

Larvae of the seed chalcid Bruchophagus kolobovae Fedoseeva develop in seeds of the two cultivated species of birdsfoot trefoil — Lotus corniculatus Linnaeus, broadleaf or upright trefoil, and L. tenuis Waldstein and Kitaibel, narrowleaf or prostrate trefoil. California growers and seedsmen have been concerned about this insect because almost nothing was known about its economic significance in this state.

The purpose of the present study was to obtain detailed information on the life history and ecology of B. kolobovae in California. Attention was given to characters that distinguished adults of this species from those of the closely related species B. roddi Gussakovskii—an important pest of seed alfalfa (Medicago saliva Linnaeus), which infests also the seeds of bur clover (M. hispida Gaertner). Cross-mating between these two chalcids was attempted.

Laboratory experiments were focused on oviposition by B. kolobovae—its duration, the choice of host, the age of acceptable seed, and the influence of light and temperature. Five larval instars were identified by head-capsule measurements, and the duration of each instar was determined under laboratory conditions.

Seasonal population trends were studied in the field and correlated with cultural practices. Data on diapause were obtained from seedpods collected weekly and held for the observation of emergence patterns. Studies of the important parasites covered their identification, seasonal histories, and significance for the control of B. kolobovae.

Historical Review

According to (Burks (1957)), 32 species have been referred to the genus Bruchophagus Ashmead, and three plant families serve as their hosts. Until recently seed chalcids developing on several species of Lotus, Medicago, and Trifolium were considered indiscriminately as a single species, Bruchophagus gibbus (Boheman), which was known previously by this and various other names—including Systole platyptera Walker and Eurytoma funebris Howard.

The Bruchophagus gibbus complex

(Kolobova (1950)) was the first to suggest that what was then called B. gibbus might be a complex of species. (Hansen (1955)) studied the host relationships of seed chalcids from alfalfa, red clover (Trifolium pratense Linnaeus), and birdsfoot trefoil. He found that each of these populations retained its host specificity and apparently would not interbreed with the others, but he felt that there was insufficient evidence to call them distinct species.