Head Capsule Width and Instar Determination for Larvae of Streblote panda (Lepidoptera: Lasiocampidae)

Abstract

The moth Streblote panda Hu¨ bner (1820) (Lepidoptera: Lasiocampidae) is an ornamental and fruit plant pest in southwestern Andalusia. Analysis of head capsule width of 387 larvae reared on different host plants (Pistacea lentisco L., Arbutus unedo L., Citrus reticulata Blanco, Retama sphaerocarpa (L.) Boiss, Spartium junceum L., Tamarix gallica L., and Vaccinium spp.) indicates that growth rate between instars does not Þt well to DyarÕs rule. The number of instars varied from 5 to 8. Head capsule width could be used directly to determine developmental stage of individual in almost all host plants used. Only for larvae fed on S. junceum, R. sphaerocarpa, Vaccinium corymbosum L. ÔSharpblueÕ, and Vaccinium ashei Reade ÔBonitaÕ, beyond third instar, did the range of measurements overlap. These data were analyzed using a combination of statistical methods. A nonlinear leastsquares approach was used to determine width means and ranges for each instar, and misclassiÞcation probabilities were calculated for each overlapping instar using Z statistics for all head capsule widths. Various factors are discussed to explain the results.