Distribution and function of girdling by caterpillars of prominent moths (Lepidoptera: Notodontidae)

Many insect species encircle stems or leaf petioles with a ring of cuts or stylet punctures, often before ovipositing beyond the girdle. Few studies have examined girdling by caterpillars. We determined the distribution of girdling in notodontid caterpillars by sleeving larvae in the field. Girdling occurred in two major branches of the Notodontidae, suggesting that the behavior evolved early in notodontid evolution or independently at least twice. Prominent girdlers included members of Schizura, Heterocampa, Hyperaeschra, and Nadata. The caterpillars typically girdled in the ultimate or penultimate instar. Girdles were produced in members of five tree families, including in oaks, hickory, elm, birch, and cherry. The frequency of girdling in our studies varied between seasons, years, and host plant species, but was not affected by switching larval food plants partway through larval development. Five-hour observations of Schizura leptinoides on pecan documented that feeding usually, but not always, occurs distal to girdles. Histology of girdle cross-sections indicated that girdling severs the phloem and cortex. We conclude that girdling behavior is widely distributed within the Notodontidae and may serve to improve leaf nutrition and/or prevent the influx of defensive compounds into leaves.