Spatial Attack Pattern, Reproduction, and Brood Development of Ips calligraphus (Coleoptera: Scolytidae) in Relation to Slash Pine Phloem Thickness: A Field Study

Ips calligraphus (Germar) spatial attack pattern, reproduction, and development were studied in 55-cm-long bolts of slash pine (Pinus elliottii Engelm. var. elliottii) with thick (3–4 mm) or thin (1–2 mm) phloem. Bolts, artificially infested with two male beetles each, were placed in the field to allow colonization by wild populations. Quadrat and distance sampling methods indicated that the spatial pattern of male attacks (nuptial chambers) was uniform (ca. 9 cm apart) on bolts of both phloem classes. Males attacked predominantly (93%) through bark crevices. Attack, gallery, egg, and brood adult densities were all positively correlated with phloem thickness. Averages of 3.3 and 3.0 parent females per attacking male were found in thick and thin phloem, respectively. Gallery systems of introduced males tended to have more total gallery length and more eggs than those of wild males in both phloem classes. Brood adults from thick phloem emerged earlier and were larger than those from thin phloem. The sex ratios of brood adults reared from thick and thin phloem were similar (ca. 45% males). Results of this field study agreed with previous laboratory studies.