Some sawfly larvae survive predator-prey interactions with pentatomid Picromerus bidens

The first complete World Catalog of sawflies (Hymenoptera, suborder Symphyta) for over 100 years is presented. It contains references to the original descriptions and provides brief distributional data for 803 genera, 8353 species (123 with two or more subspecies) and 161 subspecies in addition to the nominal subspecies. 15245 proposed names are treated, including replacement names, infrasubspecific names and nomina nuda, of which only 22 could not be checked in the original publications. Current taxonomic placement of genera and species and occurrence in zoogeographic regions are indicated. The list of names contains 31245 name combinations, variant spellings and family-group names. The authors attempted to consult all publications with taxonomic content referring to Symphyta that have appeared up to 31.12.2009. The 2960 cited references include all those that are known to contain original descriptions of taxa. Short biographical data and portraits of 168 symphytologists as well as images of representatives of extant sawfly taxa are included.

Larvae of the sawfly Neodiprion sertifer (Hymenoptera: Diprionidae), when disturbed, discharge an oily oral effluent essentially identical chemically to the terpenoid resin of its host plant (Pinus sylvestris). The resin is sequestered by the larva upon feeding, and stored in two compressible diverticular pouches of the foregut. The fluid is effectively deterrent to predators. The defensive use by an insect of a plant resin provides an instance of secondary utilization by a herbivore of the protective chemical weaponry of its host.

Gregariousness in animals is widely accepted as a behavioral adaptation for protection from predation. However, predation risk and the effectiveness of a prey's defense can be a function of several other factors, including predator species and prey size or age. The objective of this study was to determine if the gregarious habit of Malacosoma disstria caterpillars is advantageous against invertebrate natural enemies, and whether it is through dilution or cooperative defenses. We also examined the effects of larval growth and group size on the rate and success of attacks. Caterpillars of M. disstria responded with predator-specific behaviors, which led to increased survival. Evasive behaviors were used against stinkbugs, while thrashing by fourth instar caterpillars and holding on to the silk mat by second instar caterpillars was most efficient against spider attacks. Collective head flicking and biting by groups of both second and fourth instar caterpillars were observed when attacked by parasitoids. Increased larval size decreased the average number of attacks by spiders but increased the number of attacks by both stinkbugs and parasitoids. However, increased body size decreased the success rate of attacks by all three natural enemies and increased handling time for both predators. Larger group sizes did not influence the number of attacks from predators but increased the number of attacks and the number of successful attacks from parasitoids. In all cases, individual risk was lower in larger groups. Caterpillars showed collective defenses against parasitoids but not against the walking predators. These results show that caterpillars use different tactics against different natural enemies. Overall, these tactics are both more diverse and more effective in fourth instar than in second instar caterpillars, confirming that growth reduces predation risk. We also show that grouping benefits caterpillars through dilution of risk, and, in the case of parasitoids, through group defenses. The decreased tendency to aggregate in the last larval instar may therefore be linked to decreasing predation risk.