Life history traits in a parasitoid dipteran species with free living and obligate parasitic immature stages.

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

PHYSIOLOGICAL ENTOMOLOGY (PRINT)

Wiley-Blackwell

Lugar: Hoboken; Año: 2010 vol. 35 p. 160 - 167

0307-6962

The robber fly Mallophora ruficauda Weidemann (Diptera: Asilidae) is an important pest of apiculture in the Pampas of Argentina. As adults they prey on honey-bees and other insects, while as larvae are ectoparasitoids of Scarabaeidae grubs. Females of M. ruficauda lay eggs in grassland where larvae drop to the ground after being wind-dispersed and burrow underground searching for their hosts. There exists a temporal asynchrony between the appearance of the parasitoid larvae and the host, the parasitoid appears earlier than the host. This report investigates if a strategy of synchronization with the host exists in M. ruficauda and determines which of the larval instars are responsible for it. Survival patterns and duration of the immature stages of the parasitoid are investigated to determine whether there is a modulation in the development at any time that could reduce the asynchrony. Experiments are carried out to determine the survival and duration of free-living larval stada in absence of cues associated with its host. It is established that the first instar is capable of moulting to the second instar without feeding and in absence of any cues related to the host, an event unique for parasitoids. Also, the first instar of M. ruficauda moults to the second stage within a narrow temporal window, and the second instar never moults in the absence of the host. After parasitizing a host the second instar has the longest lifespan and is the more variable compared to the rest of the instars with respect to survival. All larval instars except for the last (fifth) have similar mortality rates than the second one. Additionally, it is established that the host is killed during the fourth (parasitoid) stadium and that the first and fifth larval instars develop independently of the host. Finally, possible mechanisms that could aid in compensating the asynchrony between the parasitoid and the host promoting the host-parasitoid encounter are discussed.