Anelaphus parallelus

Abstract: Sexual dimorphism among Cerambycidae (Coleoptera) may be apparent in the more robust form of the female and the relatively longer length of antennae in the male, yet there are many exceptions to this generality (Yanega 1996). For Anelaphus parallelus (Newman), Linsley (1963) reported that antennae barely surpass the apices of the elytra in males and that they seldom attain the elytral apices in females. Nonetheless, it is not clear from this description which sex to assign an individual that has the antennae nearly reaching the end of the elytra. The given size ranges for the sexes, 10–13 mm for males, 12–15 mm for females (Linsley 1963), and 8–20 mm generally (Yanega 1996), are also not useful in assigning sex to an individual. Qualities of punctures on the disc of the pronotum, reported as coarse and of uniform size in females and slightly finer and of unequal size in males, have been used to separate the sexes of species of Anelaphus Linsley (Bousquet et al. 2017), but the level of accuracy for this method is not clear. The ability to sex individuals is necessary for studies of population structure and dynamics, ecology, and management. We collected body measurements from 35 female and 37 male A. parallelus. Data were used in a discriminant analysis to determine which, if any, might successfully determine the sex of individuals in this species. Anelaphus parallelus individuals were collected as larvae in 2010, 2012, 2014, 2016, and 2018 in fallen twigs pruned from living oaks and walnuts in southeastern Pennsylvania and central New York (Brown et al. 2016; Brown and Dombroskie 2019). The appearance of the pruned twig is diagnostic, preventing potential confusion with Anelaphus villosus (Fabricius) (Gosling 1978, 1981). After emergence, each adult was examined to ensure its identity as A. parallelus. Intact individuals were haphazardly selected from these collections, and 18 standard measurements, all in mm, were taken from each of the 72 specimens through a dissecting scope. Body length, head width, elytral length, pronotal length and width, and metafemoral length were measured at 10.5X. The width of the scape at the broadest point and the length of antennomeres 1–11 individually were measured at 45X. Parameters were measured to one decimal. Antennal length and the ratio of antennal length to body length were determined from these measurements. Sex of all specimens was determined by dissection. Stepwise discriminant analysis (SAS ver 9.4, SAS Institute, Inc.) was performed to select a subset of variables from among those measured to distinguish males and females. Subsequently, a discriminant function analysis was performed on the selected subset of variables, as well as subsets of interest, and followed by cross-validation to check the accuracy of equations in distinguishing between the sexes. A discriminant function analysis determines the linear combination of variables that best separates the sexes. Cross-validation takes each observation out of the data used to determine the discriminant function, treating every data point in turn as a new, unknown observation, and then determines the accuracy of classification for each observation. Measurements of males and females were similar. On average, male antennomeres were longer than those of females, resulting in proportionately longer