Bionomics of Carmenta haematica (Ureta) (Lepidoptera: Sesiidae) Which Attacks Snakeweeds (Gutierrezia spp) in Argentina

Abstract

Abstract Adult Carmenta haematica are day-flying moths with orange (female) or clear (male) wings and a wingspan of 20 to 24 mm. Adults mated in bright sunlight. Females lived an average 2.3 days and laid an average 240 eggs each on stems and twigs of the host plant. Only 66% of the eggs hatched, mostly in the 4 h before dawn. Larvae had seven instars and reached ca. 24 mm long when full grown. Larvae entered the plant at the base of twigs or leaves or sometimes directly into the crowns. They were cannibalistic after the second instar and usually only one large larva occurred in a plant in the field. Larger larvae tunneled in the larger roots and made an exit hole in a large stem 5-8 cm above the crown where they pupated; a silken tube often protruded from the exit hole. The life cycle required ca. 139.5 days at 30°C: 15 days for the egg, 107 days for the larva, 16.5 days for the pupa, and 1 day for the adult to reach peak oviposition. Larval survival decreased below 0°C, and all larvae died after 1 day at −15°C. Larvae pupated in midsummer, adults emerged in late summer, and larvae developed during the fall, winter, and spring. The species was mostly univoltine, but the presence of some large larvae and pupae during most months indicated some variation. In the field, larvae infested 20 to 25% of medium-sized or large plants. At three locations of unusually high larval populations, the combined attack by C. haematica, other root borers, and drought killed most plants of Gutierrezia solbrigii Cabrera and Grindelia chiloensis Cabrera.