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To clarify the effects of prey density on fecundity in predatory insects, relationships between density of prey (adult flies of Phaenicia sericata) and number of eggs, preoviposition periods, and egg size were examined, using adult female mantids, Paratenodera angustipennis de Saussure. The results are summarized as follows. 1) The relationship between prey density and number of flies captured by a mantis per day was described by a Type II functional response curve. 2) The relationship between prey density and number of eggs could be expressed by a curve which rises at a decreasing rate towards an upper asymptote as the prey density increases. 3) The higher the prey density, the shorter was the preoviposition period. 4) The egg size was fixed irrespective of the prey density. 5) From the above results, we conclude that the mantids increase their fecundity by ovipositing large oothecae repeatedly at shorter intervals when prey density during their adult stage is higher. It was concluded that for a population of the mantids prey density during the adult stage is an important factor influencing its rate of increase. |
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