Notes on adult feeding and behavior of Tegrodera aloga Skinner, 1903 (Coleoptera: Meloidae)

Abstract

species, T. aloga Skinner, 1903 (Figs. 1–2), T. erosa LeConte, 1851 and T. latecincta Horn, 1891, which are found in the southwestern United States and adjoining northwestern Mexico. These three species are mostly geographically separate but are very closely related and distinguished from one another only by a combination of variable adult traits (Pinto 1975a). The range of T. aloga is primarily central to southern Arizona, with scattered records in western Arizona, extreme southeastern California and Sonora, Mexico. We here summarize the known agricultural impacts, behavior, and biology of this species and report new plant feeding records and notes from our observations. Tegrodera aloga causes occasional agricultural problems. The first reported pestiferous event in Arizona was in 1914, where “they were observed to attack the foliage of young fruit trees in addition to alfalfa” (Morrill 1914:33, reported there under the older concept of T. erosa). Again, in 1930, the beetles were noted to have defoliated unspecified vegetable crops after migrating from the surrounding desert into agricultural fields (Lebert 1931:60, reported under the name T. latecincta). Tegrodera aloga was further reported to feed on alfalfa from museum specimen labels from southeastern California and central Arizona as well as from sugar beet crops (Pinto 1975a:49). Most recently, a number of reports emerged in 2015 of T. aloga being found in organic packaged greens, specifically packaged lettuce, spinach, and salad in both Canada and the United States (Anonymous 2015, Northrup 2015). Many Nearctic species within the family of Meloidae are known to be parasites of solitary ground dwelling bees (Erickson et al. 1976). Tegrodera aloga is presumed to be such a parasite of bee nests, though no direct observations in the wild have yet been published. Triungulin (first-instar) and first-grub phase larvae have been reared from captive adults, but the subsequent coarctate larval stage was not successfully reared to pupation (Erickson & Werner 1974). The triungulin larva was described by Erickson (1973). Erickson & Werner (1974) reported that the triungulin instar lasts only 2–3 days before it molts into the first-grub phase which occupies instars 2–5. During this latter phase, the larvae fed on pollen balls created by bees. Erickson & Werner (1974) offered larvae of several bee species as food to T. aloga larvae, but none were consumed. This may indicate that T. aloga feeds only on pollen ball stores of ground nesting bees, but the failure to rear larvae all the way through to the adult stage may alternatively indicate that some other specific food source is required. Erickson & Werner (1974) concluded from their study that consuming bee larvae was not critical to the development of T. aloga, at least during the feeding instars, but moisture level within the rearing chambers and composition of the food mattered greatly. Species within Tegrodera have a unique courtship behavior among meloids, associated with their morphology, where the male and female face one another and the male begins stroking the female’s antennae with his own while moving her antennae in Scientific Note