Sympatry ofMilesia scutellataHull andMilesia virginiensis(Drury) Flower Flies¹at Their Western Range Limits in North America, and the Previously Unknown Juvenile Stages ofM. scutellata

Combined stereomicroscope and SEM disentangle the fine morphology of the undescribed larva and puparium of the hoverfly Milesia crabroniformis (Fabricius, 1775) (Diptera: Syrphidae)

“…Milesia crabroniformis lay eggs on rot holes of chestnut trees and narrow-leafed ash F. angustifolia Vahl, 1804 (Quinto et al, 2014), filled with water and debris, a fact that coincided with the other known Milesia species (Snow, 1958;Krivosheina, 2001;Fleenor and Taber, 2009;Iijima, 2016). According to Snow (1958), the larva and puparium of M. virginiensis were found on a man-made stump hole of a sweet gum tree (Liquidambar styraciflua L., 1753); the egg and larva of M. scutellata on rot holes in fire-gutted pines (Fleenor and Taber, 2009), the larva of M. tadzhikorum in a stump hole of euphrates poplar tree (Krivosheina, 2001). Milesia undulata was observed laying eggs/searching oviposition sites in rot holes of Japanese chestnut trees, Castanea crenata Siebold & Zucc., 1846 (Iijima, 2016).…”

“…Regarding M. crabroniformis, adult behaviour can be guessed from the information available on the other species of Milesia. Males of both M. scutellata and M. virginiensis show heavy territoriality around trophic resources and hilltops, or during the breeding season (Maier and Waldbauer, 1979;Fleenor and Taber, 2009), suggesting that males of M. crabroniformis may also be territorial.…”

“…Adults can be separated from those of all other syrphids by the structure of the metathoracic spiracle, which has an outer and inner row of branched hair-like structures partially closing the spiracular opening instead of only one row (Hippa, 1990). Batesian mimicry is quite usual in adults, as they mimic wasps as a defence mechanism (Fleenor and Taber, 2009;Penney et al, 2014;Speight, 2020), which is the reason why they can be misidentified by non-experts.…”

“…The larvae of this genus can be distinguished by the presence of a large group of hooks located at the front of each anterior respiratory process, consisting of 3-4 hooks on a primary row and a variable number of smaller hooks on a second and third row, as well as a second smaller group of hooks located below each of the large groups of hooks (Rotheray, 1993). Currently, the larvae of only three Milesia species have been found: M. virginiensis (Drury, 1773) in the USA (Maier, 1982;Rotheray, 1993), M. scutellata Hull, 1924 in the USA too (Fleenor andTaber, 2009), andM. tadzhikorum Peck &Hippa, 1988 in Tajikistan (Krivosheina, 2001).…”

“…tadzhikorum Peck &Hippa, 1988 in Tajikistan (Krivosheina, 2001). The larvae of all these three species have been found in tree rot holes, what leads to the assumption that the larvae of all Milesia species are saproxylic (Snow, 1958;Rotheray, 1993;Rotheray and Gilbert, 1999;Krivosheina, 2001;Fleenor and Taber, 2009). In addition, Milesia undulata Snellen van Vollenhoven, 1863, is known to use rot holes as oviposition site too (Iijima, 2016) and M. crabroniformis is supposed to breed in rot holes of Fraxinus angustifolia Vahl, 1804 in Spain due to the capture of adults with emergence traps in this breeding site (Quinto et al, 2014).…”