本文主要探討四紋豆象在面臨不同種類之寄主時,其產卵的寄主選擇反應為何?其選擇的結果是否能夠配合幼蟲的取食適應狀況,因此而能提高雌蟲本身的適應值。試驗中提供六種不同寄主包括:紅豆、綠豆、花豆、黑豆、黃豆、玉米,給予四紋豆象進行偏好試驗,寄主偏好試驗分成兩種處理,一是自由選擇試驗,即將不同種類寄主混合,目的是讓豆象在不同寄主同時存在的狀況做產卵選擇。另一則是非選擇試驗,亦即分別提供不同寄主,觀察豆象在面對單一種類寄主時的產卵行為。試驗進行後,再比較兩種處理下豆象對各寄主之產卵偏好與寄主大小或子代存活間之相關性。結果發現,自由選擇與非選擇試驗的結果有差異存在。在自由選擇試驗下,卵數與子代存活率以及卵數與寄主大小都呈現正相關的關係;在非選擇試驗下,卵數與子代存活率也同樣呈現正相關,然而,卵數與寄主大小卻無顯著相關性。因此,兩種試驗處理下,豆象的產卵選擇與子代的存活適應有顯著的正相關。而不同處理下雌蟲產卵偏好的差異,則顯示豆象在選擇不同種類寄主時有比較的行為,而此結果支持四紋豆象對不同寄主大小進行比較的相對法則(relative rule)假說。
The aim of this study was to reveal the host-choice mechanism of the seed beetle, Callosobruchus maculatus, under a condition when different hosts are provided. Also we studied how female beetles select their hosts and whether this is related to the feeding demand of their larvae. Six different species of seeds including adzuki bean, hairy dumaisa, pigeon pea, soybean, mung bean, and maize, were used in our experiments, and both free-choice and non-choice tests were conducted. In the free-choice test, six different species of seeds were provided at the same time, while in the non-choice test, hosts of each species were provided separately. In the free-choice test, both the survivorship of offspring and the host size showed a positive relationship with the numbers of eggs laid on the seed. However, in the non-choice test, only the survivorship of offspring and the numbers of eggs laid showed a positive relationship, while there was no significant correlation between seed size and the numbers of eggs laid on the seed. Taken together, these results suggest that the female can choose appropriate hosts for her offspring both in free-choice and non-choice test arenas, showing a positive relationship between host preference and survivorship of offspring in both tests. Comparison of the preference indices between free-choice and non-choice tests suggests that C. maculatus may use a relative rule to select a host on which to lay her eggs when different hosts are provided at the same time.