Laboratory Biology and Rearing of Tetrastichus brevistigma (Hymenopera: Eulophidae), a Larval-Pupal Parasitoid of the Elm Leaf Beetle (Coleoptera: Chrysomelidae)

Abstract

Tetrastichus brevistigma (Gahan) parasitized last in stars, prepupae, and pupae of the elm leaf beetle, Xanthogaleruca (=Pyrrhalta) luteola (Muller). Although T. brevistigma is deuterotokous with males constituting 3.1% of field samples, males were never observed in 21 generations reared in the laboratory. Mean longevity (±SEM) at a 15:9 (L:D) photoperiod and 25 was 21 ± 0.76d. Mean fecundity (±SEM) was 144 ±7.9 offspring. Percentage of parasitization and the number of parasitoids produced per host decreased when elm leaf beetle pupae were older than 72 h. Diapause was 3, 4, 72.5, and 46.7% at 15:9, 14:10, 13: 11, and 12:12 (photo: scotophase), respectively. The photosensitive stage of T. brevistigma appears to be the egg or first in star. Parasitized pupae could be stored at 2°C for 30 d without affecting emergence of T. brevistigma . Feasibility of mass rearing T. brevistigma is discussed.