Heat Treatment of the Adzuki Bean Borer, Ostrinia scapulalis Infected with Wolbachia gives Rise to Sexually Mosaic Offspring

A maternally inherited intracellular bacterium, Wolbachia, causes reproductive alterations in its arthropod hosts. In the adzuki bean borer, Ostrinia scapulalis (Walker) (Lepidoptera: Crambidae), naturally-occurring Wolbachia selectively kills male progeny. This Wolbachia strain appears to have a feminizing effect, since antibiotic treatment of infected female moths gives rise to male progeny with sexually mosaic phenotypes. It is proposed that male-specific death occurs through the feminizing effect, and sexual mosaics are produced when this effect is incompletely exerted. Here we examined whether the treatment of infected female moths with high temperatures (34°C, 36°C, or 38°C), which is likely to suppress the activity of Wolbachia, induces sexually mosaic progeny. It was found that eggs laid within 24 h after treatment of Wolbachia-infected mothers at 36°C gave rise to seven sexual mosaics along with 54 normal females. The time lag between treatment and the appearance of mosaic progeny was much shorter with heat treatment than antibiotic treatment, suggesting that heat treatment is more useful for spotting developmental timing when Wolbachia exerts its feminizing effect on O. scapulalis embryos.