A potential cost to environmental symbiont acquisition in the arboreal leaf-footed bug Leptoglossus zonatus

Environmental acquisition of symbionts by their animal hosts is common in marine environments but relatively rare in above-ground terrestrial systems. Unusually, true bugs in seven families, including the leaf-footed bugs (Coreidae) must ingest their specific nutritional bacterial symbiont, Caballeronia (Burkholderiaceae), early in development for optimal growth and fitness. The ingested bacteria then colonize a gut section that serves as a symbiotic organ. We have shown that the leaf-footed bug pest Leptoglossus zonatus requires Caballeronia: aposymbiotic bugs develop slowly, show elevated rates of mortality, and the few individuals that reach adulthood do not reproduce. This presents a conundrum: how do 2^nd instar nymphs of this insect, dwelling in the canopy of orchard crops (especially pomegranate, almond and pistachio) acquire this common soil bacterium? Nymphs confined in cages on pomegranate branches in an orchard over two seasons acquired the symbiont at relatively low rates, suggesting the bacterium is not ubiquitous above ground, but we could not exclude the possibility that free-roaming bugs would find their symbiont somewhere on the tree or in a trip to the soil. In fall 2024 we will introduce 2^nd instar nymphs to the canopy of caged entire trees and compare the developmental success of bugs pre-fed the symbiont (control bugs) with those that must find the symbiont on their own. Our study will provide insight into a fundamental aspect of the biology of these bugs, one that could potentially be exploited for pest management.