Abstract Systena frontalis (F.) (Coleoptera: Chrysomelidae) is an economically important pest of agricultural crops and container-grown ornamentals in the United States, yet critical aspects of its biology remain poorly understood. We quantified the biometrics of larval, pupal, and adult stages and characterized female reproductive development to support improved pest monitoring and management. To determine larval stages, larvae were extracted from growing media in containers. The larvae were then assigned to instars based on head capsule width (HCW) measurements using one-dimensional k-means clustering. Four distinct larval instars were identified with body length, 1.58 to 4.10 mm, 2.20 to 5.70 mm, 4.20 to 5.90 mm, and 6.50 to 9.50 mm as first, second, third, and fourth instars, respectively. These stages exhibited predictable increases in HCW consistent with Dyar’s rule. The pupal length averaged 3.60 ± 0.05 mm (n = 49), whereas adult females were longer than males, with 4.42 ± 0.01 mm (mean ± SE; n = 337) and 3.69 ± 0.01 mm (n = 288), respectively. Female reproductive status was categorized into 3 stages: pre-vitellogenic, vitellogenic, and post-vitellogenic, based on ovarian morphology and oocyte development. These findings provide the first biometric characterization of the larval, pupal, and adult stages, as well as of female reproductive maturation. The implications of these findings include improving phenological models, refining scouting protocols, and optimizing the timing of management tactics targeting vulnerable life stages in nursery and agricultural systems.
Vavilapalli et al. (Tue,) studied this question.