Lepidopteran Webber, Orthaga exvinacea Oviposits Amidst Conspecific Colonies: A Social Facilitation Gone Unnoticed

The present study hypothesized that sequential ovipo-sition behaviour of mango leaf webber, Orthaga exvi-nacea in/near conspecific webs, affects the cohort composition within the web as well as web density in a particular tree, resulting in a multicohort composition of webs and gregarious webbing in the orchard. The active O. exvinacea webs contained mixed cohorts of developmental stages involving eggs, larvae (I–VII in-stars) and pupae (μ = 6.50, σ² = 55.23). Taylor’s pow-er law further supported the cohort variability with fluctuating b (aggregation index) across different age groups of webs, which explained heterogeneity within the web composition. Olfactometer assays and electro-antennogram studies further revealed significant dif-ferences in the response of gravid female to volatiles of different web categories. GC-EAD identified potent chemical cues, namely (E)-2-hexenal, (Z)-3-hexen-1-ol, (Z)-3-hexen-1-ol, formate, β-ocimene, β-linalool, alloocimene, cis-3-hexenyl iso-butyrate, cis-3-hexenyl-α-methylbutyrate, δ-octalactone, (+)-α-copaene, methyleugenol, trans caryophyllene, (–)-α-gurjunene, α-humulene, (+)-aromadendrene and ledene that elic-ited antennal response in O. exvinacea female moths. Thus, the results of this study indicate that O. exvina-cea moths oviposit in/near conspecific webs pointing to the existence of social facilitation in these moths.