University of California

Laboratory studies of the biology of the alfalfa seed chalcid, Bruchophagus roddi Guss. (Hymenoptera: Eurytomidae)


Frank E. Strong

Author Affiliations

Frank E. Strong was Assistant Entomologist in the Experiment Station, Davis.

Publication Information

Hilgardia 32(3):229-249. DOI:10.3733/hilg.v32n03p229. February 1962.

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The alfalfa seed chalcid, Bruchophagus roddi Guss., a small jet-black wasp which infests Medicago, has caused alfalfa seed losses of up to 83 per cent in the western United States. Experiments conducted on the seed chalcid (actually a seed eurytomid, but commonly called a chalcid) revealed that:

Infestation was maximal when the ratio of adults to pods was 1:1, when seeds were 8 to 10 days old, when adults were fed, and when temperatures at time of oviposition were 28° to 30° C.

Although previous studies had indicated that there were no definite larval instars, this investigation revealed four larval stages, distinguished by both body and mandible lengths.

Larvae chilled at slightly below room temperature emerged more rapidly than those held at room temperature or those subjected to lower temperatures.

The greatest number of adults survived when they were fed and held at 50° F.

The species is more prolific than previously suspected, as demonstrated by the production of 86 offspring by one female during a 13-day period.

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Strong F. 1962. Laboratory studies of the biology of the alfalfa seed chalcid, Bruchophagus roddi Guss. (Hymenoptera: Eurytomidae). Hilgardia 32(3):229-249. DOI:10.3733/hilg.v32n03p229
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