Cranberry girdler (Chrysoteuchia topiaria (Zeller); Lepidoptera: Pyralidae) can be a serious pest of cranberries (Vaccinium macrocarpon Ait.), turfgrasses and conifer seedlings. Initial observations in cranberries led to the related hypotheses that: (1) when disturbed, females attempt to escape by dropping whereas males fly away; and (2) females' wings lift and carry more weight per unit of wing area than males' wings.
We tested the first hypothesis on sunny days in a cranberry field by pursuing moths, then collecting them with a modified handheld vacuum. In response to pursuit, more females than males escaped by dropping. Most of the females that dropped did so on the windiest day and on the coolest day. The two males that dropped did so on the coolest day.
We tested the second hypothesis by weighing the females and males, measuring the area of the most intact forewing and hindwing and calculating wing load. We also calculated wing load of females and males raised on reed canary grass in the lab. The wings of field-collected females lifted and carried approximately 50% more weight than those of field-collected males. Newly emerged, lab-reared moths were heavier and had larger wings than field-collected moths. The wing load of lab-reared females was approximately 67% greater than that of males.
Our results suggest that the cost of flight is greater for females than for males, and that many females drop when pursued to conserve energy and protect their load of eggs. We rarely captured unmated females or recently mated females with large egg loads, suggesting that these females remain within the canopy of cranberry foliage. Avian predators probably catch far more male than female girdlers. Females that drop to or remain near the ground may become prey of arthropods.
Species 1: Lepidoptera Pyralidae Chrysoteuchia topiaria (cranberry girdler, subterranean webworm)
Keywords: cranberry Vaccinium macrocarpon Ait, biological control
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