Ant mimicry by an aphid parasitoid, Lysiphlebus fabarum

Abstract

In Iran, Lysiphlebus fabarum (Marshall) (Hymenoptera: Braconidae: Aphidiinae) is a uniparental parasitoid of the black bean aphid, Aphis fabae Scopoli (Hemiptera: Aphididae), that possesses various highly evolved adaptations for foraging within ant-tended aphid colonies. Direct observations and video recordings were used to analyze the behavior of individual females foraging for A. fabae on bean leaf disks in open arenas in the laboratory. Females exploited aphids as hosts and as a source of food, allocating within-patch time as follows: resting - 10.4%, grooming - 8.2%, searching - 11.5%, antennation (host recognition) - 7.5%, antennation (honeydew solicitation mimicking ants) - 31.9%, abdominal bending (attack preparation) 19.7%, probing with the ovipositor (attack) - 10.8%. The mean handling time for each aphid encountered was 2.0 ± 0.5 min. Females encountered an average of 47.4 ± 6.4 aphids per hour, but laid only 1.2 eggs per hour. The ovipositor insertion time for parasitism ranged from 2 sec to longer than a minute, but most insertions did not result in an egg being laid. A. fabae defensive behaviors included kicking, raising and swiveling the body, and attempts to smear the attacker with cornicle secretions, sometimes with lethal results. Food deprivation for 4–6 h prior to testing increased the frequency of ant mimcry by L. fabarum. Females also used ant-like antennation to reduce A. fabae defensive behavior, e.g. the frequency of kicking. L. fabarum attacks primed A. fabae to be more responsive to subsequent honeydew solicitation, such that experienced females improved their feeding success by alternating between the roles of parasitoid and ant mimic. These results reveal the possibility for mutualisms to evolve between L. fabarum and the ant species that tend A. fabae, since L. fabarum receive ant protection for their progeny and may benefit the ants by improving A. fabae responsiveness to honeydew solicitation.

Body size affects host defensive behavior and progeny fitness in a parasitoid wasp, Lysiphlebus fabarum

“…Similarly, Gerling et al (1990) showed that Aphelinus asychis (Walker) preferred to attack pea aphids, Acyrthosiphon pisum (Harris), from an anterior or posterior orientation, thus reducing the effectiveness of host defensive behavior. As A. fabae feed with their stylets embedded quite deeply in plant tissues, they are unable to withdraw them quickly and tend to resort to rotating their body around their point of attachment rather than releasing the plant when attacked (Rasekh et al, 2010b). Escape appeared to be the least frequent of defensive responses (Table 3).…”

“…Cornicle secretion by aphids can be an effective defense against attack by parasitoids (Edwards, 1966;Rasekh et al, 2010b;Hopkinson et al, 2013) and predators (Acar et al, 2001;Butler & O'Neil, 2006). As cornicle droplets contain the alarm pheromone E-b-farnesene, they may yield inclusive fitness benefits by warning related conspecifics of an impending attack, even if they fail to protect the emitting individual (Wu et al, 2010).…”

“…These events included defensive behavior of the aphids such as kicking, raising and swiveling the body, withdrawing the stylet and escaping, and producing a droplet of cornicle secretion (Rasekh et al, 2010b). These events included defensive behavior of the aphids such as kicking, raising and swiveling the body, withdrawing the stylet and escaping, and producing a droplet of cornicle secretion (Rasekh et al, 2010b).…”

“…Each female was observed continuously under a stereomicroscope for 30 min and the duration of all distinguishable behavioral events was recorded using a digital voice recorder (YP-U2; Samsung, Seoul, South Korea). These events included defensive behavior of the aphids such as kicking, raising and swiveling the body, withdrawing the stylet and escaping, and producing a droplet of cornicle secretion (Rasekh et al, 2010b). The audio recordings were subsequently transcribed and used to tally female behaviors, time allocation, attack orientation, and aphid defensive responses.…”

Maternal rearing condition and age affect progeny fitness in the parasitoid waspLysiphlebus fabarum

“…The second group was kept in plastic cylinders for 72 h (old mothers) and then randomly introduced to synchronous cohorts of black bean aphid as above. The median longevity of L. fabarum females feeding on diluted honey was 4.5 days (Rasekh et al, 2010), so 72-h mothers used in this experiment were considered as old mothers. These test procedures were repeated in exactly the same manner for wasps that emerged from first (small mothers) and second (large mothers) instars.…”