Aspects of the biology of Odontria striata White included in this report are seasonal activity patterns, female reproductive development, and food-plant selection by adult beetles. Observations made during flights are noted. Flight activity commenced 30 min after sunset and lasted approximately 30 min; it was shown to be closely linked with air temperature, and a dusk temperature threshold of 6-rC is suggested. Major flight periods were found to occur during April-May (soon after eclosion) and again in August-September. Males predominated in light-trap catches; females never exceeded 20% of the total. Pitfall trapping revealed autumn and spring peaks in above-ground activity. In March, males were predominant in pitfall trap catches; through April and May females outnumbered males by 2:1 or more, but in spring and summer the sex ratio was normally closer to unity. Reasons for this pattern and exceptions to it are discussed. The female reproductive system and timing of ovary maturation are described. Ageing by reference to the degree of wear on the galeal teeth of the maxillae revealed a clear generation overlap during March-May 1980 and a less evident one the following autumn. Females were examined for presence of plant material in the crop and degree of crop distension, size of ovaries and bursa copulatrix, incidence and size of spermatophores, and numbers of mature eggs in the ovarian calyces. A small peak of mating activity in May was followed by a larger peak in August, but full maturity and fecundity were not attained until late September. Mating and egg maturation continued until late January. Analysis of crop contents of females revealed that several pasture plant species were ingested, but not necessarily in proportion to their availability in the pasture sward. Agrostis tenuis, Holcus lanatus, and Trifolium repens were favoured food plants.

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