The combined effect of host and food availability on optimized parasitoid life-history traits based on a three-dimensional trade-off surface

Beyond Hunger: A Connection Between Diet and Gonadal Development of a Ladybird Beetle

Food availability shapes morphology, physiology, growth, reproduction, and overall fitness of insects. Countless research in coccinellids reported the effect of diet in terms of quality and quantity on reproductive output. But fewer studies have reported the direct effects of food on the gonadal development in both sexes. In nature, ladybird beetle Cheilomenes sexmaculata exhibit food preference, favouring Aphis craccivora (nutritious prey) over Aphis nerii (poor prey). We hypothesized that beetles consuming nutritious prey in abundant quantity will have larger and heavier gonads. The current study assessed the effect of food preferred and its fluctuations on the gonadal development of C. sexmaculata. First instars were collected randomly from experimental stock and reared on two different diet regimes for a lifetime. After eclosion, beetles from each dietary regime were dissected daily to assess gonadal development until maturity. Here, we documented total developmental duration, body weight, weight of gonads, GSI, total area of gonads, length, and number of testicular lobules/ovarioles across different treatments. Both quality and quantity of diet significantly affected development period, body weight, and gonadal parameters in both sexes except for GSI in males and number of ovarioles in females that reared on varied diet quality, which were found to be similar. Aphis craccivora in abundant supply positively affected the growth and development of the gonads in C. sexmaculata. Beetles reared on the abundant supply of nutritious prey with larger and heavier gonads than those reared on limited supply or poor prey. This study improves our understanding of the development of gonads in ladybird beetles, which may be helpful in improving the mass rearing of ladybird beetles.

Trait-based approaches to predicting biological control success: challenges and prospects

Identifying traits that are associated with success of introduced natural enemies in establishing and controlling pest insects has occupied researchers and biological control practitioners for decades. Unfortunately, consistent general relationships have been difficult to detect, preventing a priori ranking of candidate biological control agents based on their traits. We summarise previous efforts and propose a series of potential explanations for the lack of clear patterns. We argue that the quality of current datasets is insufficient to detect complex trait-efficacy relationships and suggest several measures by which current limitations may be overcome. We conclude that efforts to address this elusive issue have not yet been exhausted and that further explorations are likely to be worthwhile.

Optimal foraging strategy to balance mixed diet by generalist consumers: a simulation model

Animals of a wide range of taxonomic groups mix various food sources to achieve a nutritionally balanced diet. The strategies they adopt to balance multiple nutrients depend on their availability in the environment. Behavioural and physiological adaptations to forage for nutrient-differing food sources have rarely been investigated in respect to nutrient availability in the environment. We developed a simulation model to explore the strategy consumers should adopt in response to the abundance of two nutritionally complementary food types. Results show that (1) consumers should invest more effort in detecting the scarce resource; (2) there is an optimized negative relationship between effort foragers should allocate to find the two types of food; (3) consumers should exhibit higher selectivity when the proportion of food types in the habitat deviates from their optimal ratio in the diet. These findings have important implications for pest control using predators that benefit from plant-based food supplements.