Chemical protection of Calvia quatuordecimguttata eggs against intraguild predation by the invasive ladybird Harmonia axyridis

Abstract

Intraspecific and interspecific predation of eggs is a well documented phenomenon amongst aphidophagous coccinellids. The invasive species Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) is known to be a top intraguild predator and reported to attack the eggs of many coccinellid species both in a laboratory setting and in the wild. A previous laboratory study highlighted that while many species' eggs were highly palatable to H. axyridis, the eggs of Calvia quatuordecimguttata (Linnaeus) (Coleoptera: Coccinellidae) appeared to be extremely well protected from attack. Here we present the results of behavioural experiments testing the hypothesis that substances on the egg surface are responsible for this protection, and report preliminary results of GC-MS analysis of these compounds. When the coatings of C. quatuordecimguttata eggs were removed using hexane, they became significantly more susceptible to predation by neonate H. axyridis larvae. However, their overall palatability was not affected, in that complete consumption was never or rarely observed. This suggests that the surface compounds are a true indicator of unpalatability in this species. The effect of hexane-washing on already palatable conspecific eggs was also analysed but had no significant effect on the susceptibility of eggs to cannibalism. We conclude that the eggs of at least one European species are effectively protected by surface deterrents from intraguild predation by H. axyridis. This effect might be due to both the diversity and abundance of hydrocarbons present within the egg coating, the presence of alkenes and/or the presence of patches of a red substance on the eggs' surface, which is thought to belong to the acid group. In conjunction with data on the susceptibility of other immature stages of C. quatuordecimguttata, this finding may indicate a decreased risk of the species falling victim to invasive H. axyridis, despite their coincident habitat ranges.

Long‐term changes in communities of native coccinellids: population fluctuations and the effect of competition from an invasive non‐native species

“…Similar increases in abundance from P1 to P2 followed by declines between P2 and P3 were recorded for C. quatuordecimguttata . Although eggs of C. quatuordecimguttata are chemically protected from predation (Ware et al ., ), competition from H. axyridis could be a possible cause of decline. Much of the research on interactions between H. axyridis and other aphidophagous species has focused on predation (Burgio et al ., ; Pell et al ., ; Ingels & De Clercq, ), however, there is considerable scope to explore competitive interactions.…”

Intraguild interactions and aphid predators: biological efficiency of Harmonia axyridis and Episyrphus balteatus

“…The alkaloids are synthesized by ladybirds and are reported to be found in all developmental stages (Ayer and Browne 1977; Hemptinne et al. 2000a,b; Agarwala and Yasuda 2001; Ware et al. 2008).…”

Mating alters the rate of development of ovarioles in the ladybird, Propylea dissecta (Coleoptera: Coccinellidae)

“…The few studies on ovariole development in ladybirds indicate that the number of ovarioles is species specifi c and dependent on the environment of developing larvae (see Hodek et al, 2011). Ferrer et al (2008 report a negative effect of suboptimal larval diet on ovariole number in A. bipunctata but the opposite trend was recorded in similar experiments on H. axyridis and a different population of A. bipunctata (Ware et al, 2008). Starvation also does not result in Harmonia axyridis developing fewer ovarioles but in a reduction in the percentage of mature ovarioles (Osawa, 2005).…”