Mating Systems and Sperm Competition in Insects

为了了解昆虫的交配系统，本文对三种昆虫的精子竞争机制进行了研究.雄性豆娘Mnais pruinosa pruinosa被观察到使用三种不同的策略，以确保交配。三种观察到的策略之间的平均交配持续时间不同，导致不同程度的精子去除和授精。对影响交配持续时间的各种因素进行了探讨。最重要的是雄性捕获配偶的地点。瓜蝇Dacus cucurbitae的雄性交配持续10小时或更长时间，通常在黎明开始并在黄昏结束。转移到雌性体内的精子数量在安装后随时间增加。交配持续时间是一个主要的决定因素，父权时，女性被双重交配。当交配间隔大于10天时，精子优先顺序出现“最后一个雄性优势”。显微镜下计数受精囊内精子数，估计精子平均寿命为17天。当第一个雄性的精子在第二次交配前死亡时，精子优先值会增加，而没有任何精子置换机制。本文研究了粘虫Leucania separata精荚大小与幼虫饲养密度的关系。在高密度条件下生长的雄性比独居的雄性产生更大的精荚，尽管它们之间的身体大小没有差异。精荚的大小增加与男性年龄或以前和当前交配之间的时间间隔。女性接受大精荚延迟再交配时间比那些接受小的。

Mechanisms of sperm competition in three taxonomical groups of insects was studied in order to understand their mating systems.1. Males of the damselfly Mnais pruinosa pruinosa were observed to use three different tactics to secure mates. The mean duration of copulation differed between the three observed tactics and resulted in varying degrees of sperm removal and insemination. A variety of factors which might influence copulation duration were invesitgated. The most important was the location of the site at which males captured thier mates.2. Males of the melon fly Dacus cucurbitae copulate for 10 hours or more, usually starting at dawn and terminating at dusk. The amount of sperm transferred to a female increased with time after mounting. Mating duration was a major determinant of paternity when females were doubly mated. However, "last male's advantage" in sperm precedence was observed when the mating interval was longer than 10 days. Counting the number of sperm in spermatheca under a microscope, mean longevity of sperm was estimated as 17 days. As a proportion of the first male's sperm die before a second mating has occurred, sperm precedence value would increase without any sperm displacement mechanism.3. Variation in spermatophore size was studied in relation to larval rearing density in the armyworm, Leucania separata. Males grew under a high density condition produced larger spermatophore than solitary males, in spite that the body size was not different between them. Spermatophore size increased with male age or time interval between previous and current matings. Females that received large spermatophore delayed remating longer than those receiving small ones.