BIONOMICS OF CARMENTA-HAEMATICA (URETA) (LEPIDOPTERA, SESIIDAE) WHICHATTACKS SNAKEWEEDS (GUTIERREZIA SPP) IN ARGENTINA

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 brig ht 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 r eached 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 w ere cannibalistic after the second instar and usually only one large l arva occurred in a plant in the field. Larger larvae tunneled in the l arger roots and made an exit hole in a large stem 5-8 cm above the cro wn where they pupated; a silken tube often protruded from the exit hol e. The life cycle required ca. 139.5 days at 30 degrees C: 15 days for the egg, 107 days for the larva, 16.5 days for the pupa, and 1 day fo r the adult to reach peak oviposition. Larval survival decreased below 0 degrees C, and all larvae died after 1 day at -15 degrees C. Larvae pupated in midsummer, adults emerged in late summer, and larvae devel oped during the fall, winter, and spring. The species was mostly univo ltine, but the presence of some large larvae and pupae during most mon ths 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 bo rers, and drought killed most plants of Gutierrezia solbrigii Cabrera and Grindelia chiloensis Cabrera.