Ericaphisvoegtlini, a new, unusual aphid species from the USA (Hemiptera, Aphididae)

Abstract Ericaphisvoegtlinisp. n. living on Chamaebatiafoliolosa (Rosaceae) in California is described based on apterous and alate viviparous females. The new species differs from all other species of the genus Ericaphis Börner, 1939 in several important morphological characters including very long and rigid dorsal setae and distinctly swollen siphunculi with clearly visible polygonal reticulation.

During work in the Aphididae collection of the Natural History Museum in London (United Kingdom) specimens of the above-mentioned Ericaphis-like undescribed species collected by David Voegtlin on C. foliosa in California, USA were found by M.
Kanturski. In addition, specimens of the same species were collected by A. Jensen on the same plant and in the same area of California in 2014.
The new species, living on Chamaebatia foliolosa from California, USA, is here described based on apterous and alate viviparous females sampled by David Voegtlin, D. Hille Ris Lambers, and Andrew Jensen.

Materials and methods
The specimens were examined using light microscope Nikon Eclipse E600 with differential interference contrast (DIC) and photographed by Nikon DS-Fi camera. The measurements were done according to Ilharco and van Harten (1987) and Blackman and Eastop (2006). Measurements are given in millimetres. The following abbreviations are used:

ANT
antennae or their lengths; ANT I-VI antennal segments I, II, III, IV, V, VI or their lengths (ratios between antennal segments are simply given as e. Diagnosis. Apterous viviparous females differ from other Ericaphis by having a well-developed quadrangular median frontal tubercle, and long and rigid dorsal setae on head, thorax, and abdominal dorsum. The siphunculus is also unusually swollen and has 4-7 rows of polygonal cells in its subapical zone. The new species shares with E. avariolosa (David, Rajasingh & Narayanan, 1971), E. leclanti Remaudière, 1971, andE. wakibae (Hottes, 1934) some features of the siphunculus (e.g. slightly swollen with row(s) of polygonal cells in the subapical zone) but differs in the other above-mentioned characters.  Description. Apterous viviparous female (n = 34). Colour in life: dark green. On slide: body in general sclerotised, pale yellow to yellow. ANT yellow with brown distal part of ANT IV and whole ANT V-VI. Tibiae yellow with brown to dark brown distal parts (but the very apex of tibiae lighter). Tarsi light brown to brown. SIPH pale to yellow basally and brown to dark brown distally (Figure 1a).
Alate viviparous female (n=22). Colour in life: unknown. On slide: head and ANT light brown to brown with basal part of Ant III and PT lighter. Pronotum light brown, rest of thorax brown. Wings hyaline with light brown veins (cubital veins slightly darker). Femora brown with pale proximal part and dark distal part. Tibiae yellow to light brown with brown to dark distal part. Abdomen with brown sclerotisation, SIPH brown with lighter apical part, cauda brown (Figure 1b).
Etymology. The authors have the pleasure in naming the new species to honour Dr. David Voegtlin, an aphid specialist from the Illinois Natural History Survey (University of Illinois, Urbana-Champaign, USA), who was also the first collector.
Biology and distribution. The new aphid species is associated with Chamaebatia foliolosa Benth. (Rosaceae). Its sexual morphs and life history are unknown, but probably it is monoecious holocyclic. The aphid species is presumably endemic to California, as is its host plant.

Discussion
Appropriate generic placement of this species was challenging due to its unusual features, including its prominent median frontal tubercle, robust dorsal setae, and swollen reticulated siphunculi. It was tempting to consider this aphid the first of a new genus. In the end we opted for placement in Ericaphis for a few reasons. First, E. voegtlini shares important features with most Ericaphis, including the presence of a median frontal tubercle (albeit more extreme), typically two pairs of lateral setae on the cauda (plus one dorso-apical seta), dorsal pigmented abdominal patch in the alate vivipara, no secondary rhinaria on antennal segment III in the apterous vivipara, and relatively few and large secondary rhinaria on antennal segment III in the alate vivipara. Second, there are western North American species scattered among at least three genera (Aulacorthum, Ericaphis, and Wahlgreniella) that share many features and that may be closely related. Ideally, the generic classification of these aphids should be done as a more comprehensive study, using all the similar and related species currently placed in these, and possibly other, genera. Third, the aphids of western North America are still in need of basic discovery work in the field. The second author spends hundreds of hours each year collecting aphids and making field observations, and has discovered, and continues to discover, many new species and host plant relationships (see http://aphidtrek. org/), including isolated samples and observations of aphids related to the above-mentioned genera. Comprehensive analysis of the relevant generic classification, therefore, is best delayed until more of the currently undescribed and undiscovered aphid species are documented and described. In the meantime, E. voegtlini is a distinctive, easily recognised species that feeds on an unusual plant with a very limited distribution, and interim placement of it in Ericaphis is a practical choice. We hope that by publishing its description we will draw attention to the possible undiscovered diversity of this aphid group in North America.