Life History Plasticity and Gregarious Cocooning Behavior of the Wild Silkmoth Cricula trifenestrata Helfer (Lepidoptera: Saturniidae) on a Novel Host Plant, Cinnamon, in Thailand

<i>Cricula trifenestrata</i> Helfer was recently documented on cinnamon (<i>Cinnamomum</i> spp.), a novel host plant in Thailand. We compared life history and behavior under natural field, semi-natural caged, and laboratory conditions on cinnamon, plus opportunistic collection from hog plum (<i>Spondias pinnata</i>). Laboratory rearing significantly extended development (62.30 ± 3.68 days) versus field conditions (56.30 ± 1.83 days, <i>p</i> < 0.001) through delayed egg and pupal stages, indicating life history plasticity. We discovered density-dependent oviposition plasticity (linear arrangements in field: 155.6 ± 84.9 eggs/batch; clustered in laboratory) and novel gregarious cocooning behavior, where 85.1% of individuals (<i>n</i> = 47 sites) aggregated to form communal clusters with unique reticulated architecture. Female cocoon shell ratio (CSR) was significantly higher in laboratory (5.02 ± 0.72%) and hog plum cohorts (5.30 ± 0.30%) than field conditions (3.92 ± 0.51%, <i>p</i> = 0.002). Opportunistic rearing yielded >2 kg fresh cocoons, with clusters reaching 0.220 kg. These findings establish biological baselines for <i>C. trifenestrata</i> Helfer on cinnamon, reveal sophisticated social behaviors expanding lepidopteran sociality concepts, and demonstrate commercial potential for sustainable sericulture integrated with pest management.