Barrantes M E, Castelo M K
Grupo de Investigación en Ecofisiología de Parasitoides (GIEP), Departamento de Ecología, Genética y Evolución, Instituto IEGEBA (CONICET-UBA), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Intendente Güirales 2160, Ciudad Universitaria, Pabellón II (C1428EHA), Ciudad de Buenos Aires, Argentina.
Bull Entomol Res. 2014 Jun;104(3):295-306. doi: 10.1017/S0007485314000029. Epub 2014 Feb 19.
Larvae of the robber fly Mallophora ruficauda are ectoparasitoids of white grubs and adults are an important apiculture pest in Argentina. Females oviposit on tall grasses and the second instar larva actively searches and locates hosts. There are nine potential hosts in the distribution area of this parasitoid and Cyclocephala signaticollis (Coleoptera: Scarabaeidae) is the most parasitized in the field. However, M. ruficauda has a certain degree of behavioural flexibility towards different host species, and not being a strict specialist. The conditions under which the parasitoid orientates and accepts different hosts' species are unknown. We studied the host specificity of M. ruficauda towards three species of Cyclocephala genus and we determined whether this specificity depends on larval age. We also evaluated whether larva orientation towards Cyclocephala species changes with chemical cue concentration. We assessed host specificity measuring the orientation and acceptance behaviours towards kairomones extracts and live individuals of Cyclocephala species using M. ruficauda larvae of low and high life expectancy (i.e., young and aged second instar larvae). We observed that young larvae orientated only towards C. signaticollis chemical stimulus, whereas aged larvae orientated also towards C. modesta, and the same was observed with increasing stimuli's concentration. Both young and aged M. ruficauda larvae orientate towards live C. signaticollis and C. putrida species and rejected C. modesta. Also, we found that larvae accepted all Cyclocephala hosts. In conclusion, our results indicate that specificity in the laboratory, observed through host orientation and host acceptance behaviours, depends not only on the availability of host species, but also on the nature of the host's stimuli combined with parasitoid age.
盗虻Mallophora ruficauda的幼虫是蛴螬的体外寄生蜂，其成虫是阿根廷重要的养蜂害虫。雌虫在高草上产卵，二龄幼虫会主动搜寻并定位寄主。在这种寄生蜂的分布区域内有九种潜在寄主，而Cyclocephala signaticollis（鞘翅目：金龟科）是田间被寄生最多的寄主。然而，M. ruficauda对不同寄主物种具有一定程度的行为灵活性，并非严格的专一性寄生蜂。这种寄生蜂定向并接受不同寄主物种的条件尚不清楚。我们研究了M. ruficauda对Cyclocephala属三种物种的寄主专一性，并确定这种专一性是否取决于幼虫的龄期。我们还评估了幼虫对Cyclocephala物种的定向是否会随化学信号浓度的变化而改变。我们通过测量低和高预期寿命的M. ruficauda幼虫（即年轻和老龄二龄幼虫）对Cyclocephala物种的信息素提取物和活体的定向及接受行为，来评估寄主专一性。我们观察到，年轻幼虫仅对C. signaticollis的化学刺激有定向反应，而老龄幼虫也会对C. modesta产生定向反应，并且随着刺激浓度的增加也观察到了同样的情况。年轻和老龄的M. ruficauda幼虫都会对活体C. signaticollis和C. putrida物种产生定向反应，并排斥C. modesta。此外，我们发现幼虫会接受所有Cyclocephala寄主。总之，我们的结果表明，通过寄主定向和寄主接受行为在实验室中观察到的专一性，不仅取决于寄主物种的可获得性，还取决于寄主刺激的性质以及寄生蜂的龄期。
