Voltinism and Diurnal Emergence-Flight Patterns of Ips Calligraphus (Coleoptera: Scolytidae) in Florida

Abstract

Field studies revealed that Ips calligraphus (Germar) may complete up to nine generations during a 1-year period in north-central peninsular Florida. Brood development took place in felled trees of slash pine, Pinus elliottii Engelmann var. elliottii, with thick phloem (2.5-3.5 mm; i.e., >adult pronotal width). Generational times ranged from 27 days in the summer to 81 days in the winter. Generally, female brood adults emerged earlier than did males of the same cohort; the male:female ratio was ca. 1:1.2. Adult emergence-flights occurred as a single peak during late afternoon in spring (mostly from 1500-1700 h EST) and fall (1400-1700 h), compared to near midday in winter (1200-1400 h), emergence-flights were bimodal during summer with activity peaking in early morning (0700-0900 h) and early evening (1700-1900 h). An average of 457@*D (day-degrees) above a 10@*C (822 @*D above 50 @*F) threshold were accumulated per generation using the mean-minus-threshold method of day-degree estimation. Based on weather records for Florida, the theoretical number of generations per year in slash pine trees with thick phloem was estimated to vary from as few as 7 near Pensacola to as many as 12 in the Florida Keys.