Egg-laying decisions based on olfactory cues enhance offspring fitness in Stomoxys calcitrans L. (Diptera: Muscidae)

Abstract

Selection of oviposition substrate is critical in holometabolous insects. Female stable flies, Stomoxys calcitrans , locate and select vertebrate herbivore dung in which they lay their eggs. However, the preference for vertebrate herbivore dung by S . calcitrans females, its fitness consequences for offspring, and the semiochemicals used to locate and select oviposition substrates remain unclear. Using oviposition choice tests and life table bioassays we found that gravid female S . calcitrans prefer to oviposit on donkey and sheep dung, which also improves the performance of their offspring. GC-MS analysis followed by random forest classification identified β-citronellene and carvone as the most important predictive volatile organic compounds of donkey and sheep dung, respectively. In multiple choice oviposition bioassays, S . calcitrans laid more eggs in wet sand containing β-citronellene and carvone than in other treatments. The attractiveness of these compounds was confirmed in a field trial, with traps baited with β-citronellene and carvone catching more S . calcitrans . We conclude that gravid female S . calcitrans use semiochemical cues to choose oviposition substrates that maximise offspring fitness.

Larval experience of stable fly, Stomoxys calcitrans Linneaus, 1758 (Diptera: Muscidae) does not influence oviposition preference in gravid females

“…Consequently, our study found no evidence in support of the HHSP. Our results imply that preference for particular dung types by female S. calcitrans for oviposition (Baleba et al, 2019) is an innate rather than learned behaviour. Rojas and Wyatt (1999) demonstrated that experience of the cabbage moth caterpillar Mamestra brassicae (Lepidoptera: Noctuidae) did not affect oviposition behaviour of their females.…”

“…During all the bioassays, we used camel and sheep dung as rearing substrate based on the difference in their physicochemical properties (Baleba et al, 2019) The amount of substrate in each test arena was 50 g. At 10 min after setting up each replicate, larvae found on a substrate were considered to have made a choice.…”

“…We did not use organic solvents because they could be toxic to the larvae or represented a source of contamination. During all the bioassays, we used camel and sheep dung as rearing substrate based on the difference in their physicochemical properties (Baleba et al, 2019)…”

“…Trypanosoma evansi, Besnoitia besnoit), and helminths (e.g. Baleba et al (2019) demonstrated that gravid females of S. calcitrans preferred to oviposit on donkey and sheep dung over camel and donkey, which led to greater fitness in pre-imaginal stages. During outbreaks, S. calcitrans can reduce weight gain in cattle by up to 19%, and lead to a 40-60% reduction in milk yield (Carn, 1996;Walker, 1990).…”

“…Eggs are laid and the larval stage (with three instars) and pupal stage are completed in the dung of herbivorous animals such as cows, donkeys, horses, goats, and sheep (Hafez & Gamal-Eddin, 1959;Jeanbourquin & Guerin 2007;Cançado et al, 2013). Baleba et al (2019) demonstrated that gravid females of S. calcitrans preferred to oviposit on donkey and sheep dung over camel and donkey, which led to greater fitness in pre-imaginal stages. In this study, we investigated whether this preference-performance behaviour was fixed or whether it was influenced by experience of S. calcitrans larvae gained throughout their development.…”