Insights to the host discrimination and host acceptance behavior in a parasitoid (Diptera: Asilidae): Implications on the fitness.

CRESPO. J.E.; CASTELO, M.K.

Palermo

Conferencia; Conference on “Behavioural Ecology of Insect Parasitoids: a perspective”; 2009

European Science Foundation

<!-- /* Font Definitions */ @font-face {font-family:"Nimbus Roman No9 L"; mso-font-alt:"Times New Roman"; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:0 0 0 0 0 0;} @font-face {font-family:"DejaVu Sans"; mso-font-charset:0; mso-generic-font-family:auto; mso-font-pitch:variable; mso-font-signature:0 0 0 0 0 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0pt; margin-bottom:.0001pt; mso-pagination:none; mso-hyphenate:none; font-size:12.0pt; font-family:"Nimbus Roman No9 L"; mso-fareast-font-family:"DejaVu Sans"; mso-bidi-font-family:"Times New Roman"; mso-font-kerning:.5pt; mso-ansi-language:ES-AR;} @page Section1 {size:595.25pt 841.85pt; margin:113.4pt 70.85pt 113.4pt 70.85pt; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> The robber-fly Mallophora ruficauda is one of the principal apiculture pests in the Pampas region of Argentina. As adults they prey on honey bees and other insects, while as larvae they are solitary ectoparasitoids of third instar scarab larvae. Females of M. ruficauda lay eggs away from the host in tall grasses. After being dispersed by the wind, larvae drop to the ground, where they dig in search of their hosts. It is known that second instar larvae of M. ruficauda exhibit active host searching behaviour towards its preferred host, third instar larva of C. signaticollis. Although solitary, there are frequently cases of superparasitism in the field. It has been studied the means by which host-location occurs, yet no information about host discrimination and host acceptance is available. Since there is a habitat mismatch between parasitoid larva and host, field studies and behavioural experiments in the laboratory were done to determine if M. ruficauda is capable of quality host discrimination. We also studied if this parasitoid is capable of conspecific detection in order to avoid superparasitism. Finally, field conditions by which superparasitism is accepted by the seeking larva were analyzed. We report that the second instar larva of M. ruficauda is capable to discriminate the parasitism status of the host by means of chemical cues, but is not capable of detecting conspecifics prior to host attack. Also, the host may not detect the presence of the parasitoid by means of chemical cues, so no counter-defense against parasitism could occur. Furthermore, we have determined that superparasitism happens on the heavier hosts which could harbor several parasitoid individuals. All in all, it seems that M. ruficauda can discriminate and decide whether to accept superparasitism or wait for a best host. The decisions that larvae make could influence greatly the fitness of adults.