Diet and chemical defence in ladybird beetles (Coleoptera: Coccinellidae)

In this paper, I review the effects of the diet of ladybirds on chemical defence in this group of beetles. The tendency to refl ex bleed and the diversity of autogenously produced alkaloids in different taxa may be evolutionarily related to diet and the likelihood of food limitation. Within predatory species, both prey quantity and quality have been shown to affect autogenous alkaloid production. A few ladybird predators have been suggested to adaptively sequester toxins from their prey for their own defence. However, in most cases the evidence for this is limited, with questions remaining about the costs of accumulated toxins and their defensive value, especially over and above pre-existing autogenous defence. Only a single case (Hyperaspis trifurcata and carminic acid) is well supported. In the case of ladybird predators acquiring pyrrolizidine alkaloids from the ragwort aphid Aphis jacobaeae, I show that toxin accumulation is not very costly and the aphid is even an essential prey for some ladybirds. However, the defensive value of pyrrolizidine alkaloids to ladybirds is still not investigated. Intraspecific diversity in autogenous chemical defence could be reinforced further if chemical protection is conferred via sequestered chemicals. However, to understand better how ladybird diet and chemical defence interact, we need a clearer grasp of how the defensive chemicals of food are resisted or tolerated by ladybirds.

Automated summary

This paper reviews the effects of ladybird diet on chemical defense in this group of beetles, including autogenous production of alkaloids and sequestration of toxins from prey. The evidence for predators sequestering toxins from their prey is limited, and further research is needed to understand the costs and defensive value of accumulated toxins. The defensive value of pyrrolizidine alkaloids acquired from the ragwort aphid by ladybird predators is still not well-investigated. Additionally, understanding how ladybirds resist or tolerate defensive chemicals in their food is crucial to better understand the interaction between ladybird diet and chemical defense.