Reduction of oviposition time and enhanced larval feeding: two potential benefits of aggregative oviposition for the viburnum leaf beetle

Abstract

1. Although aggregation in non-social arthropods is common, its adaptive value is not always clear. Oviposition behaviour of the viburnum leaf beetle (Pyrrhalta viburni ) is aggregative, with females preferring to lay eggs on twigs already infested by conspecifics. We previously showed that aggregative oviposition aided in overcoming host plant defences. Here we explore two additional benefits of this behaviour: reduction of time investment in oviposition; and improvement of host use by larval group feeding.2. In video-recorded trials, the presence of conspecific egg masses did not have an impact on the time associated with oviposition, but it did affect females' preoviposition behaviour: the length of foraging movements was 21% shorter on infested than on non-infested twigs, and was concentrated near the infested area.3. In two separate studies of insect performance, larvae were reared to maturity in groups of different densities (five or 10, and five or 20, respectively) on several hosts (four and 17 Viburnum spp., respectively). Independent of host species, adults were > 13% heavier (groups of 10 vs. five), and pupation success was 27% higher (groups of 20 vs. five) at higher larval density.4. Two additional effects were dependent on host species: larval survivorship (groups of 10 vs. five), and adult mass (groups of 20 vs. five). These effects were not associated with plant defensive traits (i.e. trichomes or leaf toughness), but adult mass was associated with host nutritional quality (i.e. foliar nitrogen content).5. These results show that several traits of P. viburni larval performance are positively density-dependent, and suggest that benefits of group feeding could have played a role in the evolution of oviposition behaviour in P. viburni . Our results also demonstrate that plant quality can mediate benefits of aggregation, underscoring the importance of ecological context in understanding the feeding strategies of insects.

Plant responses to butterfly oviposition partly explain preference–performance relationships on different brassicaceous species

“…The insect oviposition mode can have a significant impact on egg survival and larval performance. When eggs are laid in clusters, neonate larvae often show gregarious feeding behavior, which benefits offspring performance in some insect species (Denno and Benrey 1997;Clark and Faeth 1998;Fordyce 2003;Allen 2010;Desurmont et al 2014;Martínez et al 2017). On the other hand, many herbivorous insects lay single eggs, spreading them over a larger area, possibly as a means of reducing predation risk and competition (Root and Kareiva 1984;Nufio and Papaj 2001).…”

Switched after Birth: Performance of the Viburnum Leaf Beetle [Pyrrhalta viburni (Paykull)] after Transfer to a Suboptimal Host Plant

“…One complicating factor that our study does not address is the recently reported observation that P. viburni benefits from larval group feeding [ 28 ]. Although P. viburni larvae do not feed gregariously in the strict sense [ 29 ], they do tend to form loose groups feeding on the undersides of young Viburnum leaves, a behavior that is facilitated by the fact that egg masses from adult P. viburni are often laid in clusters along infested twigs [ 30 ].…”

“…Although P. viburni larvae do not feed gregariously in the strict sense [ 29 ], they do tend to form loose groups feeding on the undersides of young Viburnum leaves, a behavior that is facilitated by the fact that egg masses from adult P. viburni are often laid in clusters along infested twigs [ 30 ]. Larval density was shown to be positively correlated with pupation success and, under certain conditions, adult weight on a range of Viburnum hosts [ 28 ]. Thus, larval density may play a role in the success of host-switching in P. viburni and, conversely, results of the choice-tests could have been different if larvae had been tested individually.…”

Attraction of Melitaea cinxia Butterflies to Previously-Attacked Hosts: A Likely Complement to Known Allee Effects?

“…It is not surprising, then, that ovipositing herbivorous insects show a diversity of responses to conspecifics that affect group size, ranging from aversion through neutrality to conspecific attraction. Conspecifics can enhance oviposition, either directly by their presence or indirectly, by their modification of plant quality (Judd & Borden 1992, Navasero & Ramaswamy 1993, Prokopy & Reynolds 1998, Raitanen et al 2014, Desurmont et al 2014, Durisko et al 2014. However, by far the most frequently reported effect is that insects tend to avoid host plants that bear conspecific eggs or larvae (Rothschild & Schoonhoven 1977, Williams & Gilbert 1981, Shapiro 1981, Roitberg & Prokopy 1987, Pettersson 1992, Kumari et al 2016.…”

“…Prokopy and Reynolds (1998) and Papaj et al (1992) suggested that adult female Mediterranean fruit flies cue in to the presence of other conspecific adults as an indicator of host plant quality, using "public information" (Danchin et al 2004) in a manner analogous to the phenomenon of "mate copying" in which females increase their preference for individual males after observing them being accepted by other females. Herbivorous insects may benefit from large group size by enhancement of antipredator defence (Lawrence 1990, Hunter 2000, Riipi et al 2001, by being better able to overcome host defences (Clark & Faeth 1997, Campbell & Stastny 2014, Desurmont et al 2014 or by constructing better protection against harsh climate (Kuussaari et al 2004, Kuussaari & Singer 2017.…”