Predation on adult Aphytis parasitoids in the field

Abstract

We report on predation on adult females of the parasitoids Aphytis aonidiae and A. vandenboschi (Hymenoptera: Aphelinidae) foraging in the field. During 89.6 h of observation, we witnessed 18 encounters with predators, 6 of which resulted in parasitoid capture. Three classes of generalist predators attacked Aphytis: spiders (unidentified Salticidae and Thomisidae), workers of the Argentine ant, Linepithema humile, and nymphs of the assassin bug Zelus renardii (Hemiptera: Reduviidae). Although observations were conducted during most months of the year, encounters with predators occurred only during September, October and November. During these months, encounters with predators occurred on average every 3.2 h of observation, with one in three encounters resulting in parasitoid capture. Peaks in predation coincided with population peaks of A. aonidiae, but were unrelated to population dynamics of any of the predators. We compare these results with previously published laboratory studies on longevity of Aphytis parasitoids, and conclude that predation pressure has the potential to severely limit parasitoid fitness in the field.

Predation or scavenging? Thoracic muscle pH and rates of water loss reveal cause of death in arthropods

“…When predators are small or highly mobile, for example, direct observation of predation becomes nearly impossible (Hagler et al, 2004). Furthermore, the effort required to detect even a few direct instances of predation, which typically involve multiple species of predators (Heimpel et al, 1997;Rosenheim et al, 1999), makes it difficult to obtain sample sizes large enough for meaningful statistical inference. For these reasons, ecologists rely heavily on PCR-based methods (Symondson, 2002;Sheppard et al, 2004;Foltan et al, 2005;King et al, 2008) and stable isotope analyses (Kelly, 2000;Fiedler et al, 2007;Hood-Nowotny and Knols, 2007) to characterize species interactions and to infer trophic level.…”

The Effect of Resource Aggregation at Different Scales: Optimal Foraging Behavior ofCotesia rubecula

“…Actual field mortality rates from any of these factors are largely unknown (Heimpel et al 1997). However, field experiments on Aphytis parasitoids suggest that predation rivals starvation and extreme temperature conditions as sources of mortality (Heimpel et al 1997). We do not expect that the qualitative results of our model will be affected by choosing a life expectancy that is too long.…”

Ants, pests and natural enemies in Mediterranean citrus. Ecological interactions and practical implications for biological control

“…In fact, Moreno et al (1987) In previous studies examining the impact of the ants on populations of honeydew producing Hemiptera, lower parasitism rates were reported on plants with ants relative to plants without ants (DeBach et al, 1951;Bartlett, 1961;Itioka & Inoue, 1996b, 1999. Moreover, in the case of non-honeydew producing Hemiptera, several studies showed that ants may disrupt parasitoid activity (DeBach et al, 1951;Flanders, 1958;Murdoch et al, 1995;Heimpel et al, 1997a;Martínez-Ferrer et al, 2003). Recently, a study conducted on Australian citrus revealed that the parasitism of CRS by Encarsia perniciosi (Tower) and Encarsia citrina Craw (Hymenoptera: Aphelinidae) was severely reduced in the presence of the ant Iridomyrmex rufoniger (Lowne) (Dao et al, 2014).…”

“…are highly susceptible to ant aggression. In fact, there are studies demonstrating that ants prey upon them in the field (Heimpel et al, 1997a) or disturb them during host-feeding and oviposition (Martínez-Ferrer et al, 2003). Aphytis melinus females spend more than 300 seconds per honeydew feeding bout (Tena et al, 2013b).…”

“…These interactions play an important role in agricultural ecosystems since biological control provided by the third trophic level may be negatively affected by ant activity (Flanders, 1945;DeBach et al, 1951;Heimpel et al, 1997a;Martínez-Ferrer et al, 2003).…”