Microenvironmental analysis of two alternating hosts and their impact on the ecological adaptation of the horned sumac gall aphid Schlechtendalia chinensis (Hemiptera, Pemphiginae)

The aphid Schlechtendalia chinensis(Bell) induces horned galls on their primary host Rhus chinensis(Mill). These galls serve as closed habitats to support thousands of aphids per gall. Ecological parameters inside a gall are unknown. In this study, we showed that the microclimate inside galls was reltively stable, with nearly 100% humidity and 30–50 lux light regardless of outside environmental conditions. Gall-residing aphids produce waste gas and honeydew. A gall contained 26 organic volatiles inside with acetic acid as the largest component. Honeydew is rich in sugars and may provide nutrients for microbial growth. However, no evidence for pathogenic microorganisms was found inside a gall. The acidic environment in a gall may curb microbial growth. On the secondary host, the moss Plagiomnium maximoviczii (Lindb.) T. J. Kop., the microclimate is unstable and humidity fluctuated at 45~100%, while light ranged from 150 to 500 lux on different environmental conditions. Aphid alternated in two different habitats, the gall generation increased from a single fundatrix to thousands of aphids, however, survival rate of the moss generation is less 3%. A comparison of the environmental traits between gall and moss revealed that a stable habitat with dark and moist is advantageous for aphid reproduction.