カクムネコナヒラタムシCathartus quadricollis　の増殖に及ぼす密度効果

Some biologies of the square-necked grain beetle, Cathartus quadricollis (Guer.) were investigated. The minimum preoviposition period of the species was 3 days. The effect of crowding on the rate of reproduction was examined. The average number of progeny produced decreased rapidly with the increase of parent density. The species is highly sensitive to overcrowding. At nearly all the densities high female sex ratio was obtained. The developmental period did not differ between sexes. At the higher densities the beetle seems to be a little delayed in development. Considering the origin and evolution of the species, it is suggested that the species may be of fruit- and/or seed - infesting species origin and seems to still rest on the early stage of becoming a serious pest of stored - products ; it may be r-strategist.