Fatty acids derived from oviposition systems guide female black soldier flies(Hermetia illucens)toward egg deposition sites

The black soldier fly,Hermetia illucens,comes with big promises for industrial purposes since its larvae feed polyphagously on a broad spectrum of organic substrates.However,research focusing on adult flies is scarce,which is inconsistent with their reproductive relevance within the rearing cycle.In particular,directed oviposition is a challenge in artificial systems.Currently,decomposing organic matter is commonly used as oviposition substrate,which has extensive potential for improvement in view of the lack of standardization and the risk of microbial contamination.Here,we identified three fatty acids and one fatty acid methyl ester derived from the surface of old oviposition sites and targeted to elucidate their effect on preference behavior and oviposition site selection using Y-olfactometry and prepared oviposition sites,respectively.Exposure to tetradecanoic acid attracted gravid females and stimulated oviposition most strongly,while decanoic acid demonstrated a repulsive effect.Females kept in mixed-sex populations were attracted by tetradecanoic acid,resulting in a higher egg mass found in the compound box(3.0–11.4 fold),a≥2.3 fold reduction of nonspecifically deposited eggs,and the highest total egg mass.Conversely,decanoic and dodecanoic acid caused females to lay a greater proportion of eggs nonspecifically outside both boxes.Our data suggest that fatty acids,especially tetradecanoic acid,are important cues for oviposition site selection in black soldier flies.In order to achieve a directed oviposition behavior,the role of further short-and long-chain fatty acids as attractants should be examined.

Effects of mummy consumption on fitness and oviposition site selection on Harmonia axyridis

Intraguild predation(IGP)has been commonly reported between predators and parasitoids used as biological control agents as predators consuming parasitoids within their hosts.However,the effect of parasitoid-mummy consumption on the fitness of the predator and subsequent oviposition site selection have not been well studied.In our study,we conducted two laboratory experiments to examine the influence of Aphidius gifuen-sis Ashmead(Hymenoptera:Braconidae)mummies as prey on fitness and subsequently oviposition site selection of Harmonia axyridis(Pallas)(Coleoptera:Coccnellidae).Re-sults indicate that when H.aryridis was reared on A.gifiuensis mummies only,its larval development was prolonged,and body weight of the 4th instar larvae and newly emerged adults,and fecundity decreased.Moreover,H.axyridis did not exhibit oviposition pref-erence on plants infested with unparasitized aphids or aphids parasitized for shorter than 9 days.However,compared with plants with mummies(parasitized≥9 days),H.axryridis laid more eggs on plants with unparasitized aphids.In contrast,H.axryridis previously fed with A.gifuensis mummies did not show a significant oviposition preference between plants with unparasitized aphids and those with mummies(parasitized≥9 days).Overall,our results suggest that mummy consumption reduced the fitness of H.axyridis.Although H.axyridis avoided laying eggs on plants with A.gifuensis mummies,prior feeding ex-perience on A.gifuensis mummies could alter the oviposition site preference.Thus,in biological control practice,prior feeding experience of H.axyridis should be carflly considered for reduction of IGP and increase of fitness of H.axyridis on A.gifuensis.

Breeding ecology and oviposition site selection of blackspotted pond frogs (Rana nigromaculata) in Ningbo, China

The black-spotted pond frog(Rana nigromaculata)is one of the most widely distributed species in China.However,there have been only a few qualitative descriptions of their breeding ecology and oviposition site selection.From 2004 to 2006,we investigated the breeding ecology and oviposition site selection of R.nigromaculata in Ningbo,China,quantitatively.Analyses of breeding ecology show that:(1)mean frog density in the breeding season was 0.0903±0.0029 individuals per meter(n=11)(mean±SE);(2)R.nigromaculata was a sexually dimorphic species,with females significantly larger than males in both body weight and snout-vent length;(3)the clutch size averaged 4643.04±235.96 eggs(range 1546–7897,n550);and(4)the egg size ranged from 1.50 to 1.74 mm in diameter,with an average egg size of 1.6050±0.0046 mm(n=226).Oviposition sites differed significantly from random sites in percentages of water,bare ground and vegetation cover,water depth(cm),water temperature(uC)and water turbidity.Rana nigromaculata preferred microhabitats with higher percentages of water and vegetation cover,while it avoided microhabitats with deeper water.The results suggest that microhabitats with higher percentages of water and vegetation cover,but not deeper water,should be priorities for protection and conservation of the breeding habitats of R.nigromaculata.