Biology and Food Habits of the Invasive Snail Allopeas gracile (Gastropoda: Subulinidae)

Abstract

The biology of the widely occurring but poorly known terrestrial snail Allopeas gracile (Hutton, 1834) (Gastropoda: Subulinidae) was determined, emphasizing food relationships. Isolated snails reproduced without cross fertilization. These snails deposited small clusters of eggs (3-7 per d) totaling about 20 per mo once oviposition commenced (after about 50 d). The snails grew rapidly for 50 d, attaining a mass of about 25 mg, then grew more slowly, eventually attaining a mass of about 50 mg after 250 d. Hatching occurred over a wide range of temperatures. The mean duration of the egg stage decreased from 18.7 to 8.0 d as the temperature increased from 19.5 to 32.0 °C. Allopeas gracile was omnivorous, feeding on green plants (vegetables, weeds, and flowers), fungi (cultivated mushroom and sooty mold), and animal matter (dead cockroaches and earthworms), but not decaying vegetation (tree leaves). Although this species is omnivorous, many plants allowed only maintenance, not fostering rapid growth. These small snails consumed only about 1.5 cm2 per d of favored food (lettuce) at maturity, and considerably less of most plants offered. This invasive snail does not seem to be destined to be a significant pest except perhaps under restricted circumstances.