A new species of Megoura (Hemiptera, Aphididae) from Japan

Abstract A new species of the genus Megoura, M. lathyricola sp. n., was collected from Lathyrus japonicus subsp. japonicus (Leguminosae) in seashore areas of northern and southern Japan. This species is described and illustrated, and a revised key to the identification of the world species of Megoura is presented.

Until now, three species of the genus Megoura have been reported from Japan; M. crassicauda, M. lespedezae, and M. brevipilosa. Recently, we collected a macrosiphine aphid species from the leguminous plant Lathyrus japonicus subsp. japonicus, in Hokkaido (northern Japan) and Nagasaki Prefecture (southern Japan). This species has morphological characters in common with the genus Megoura, such as swollen siphunculi, smooth head, and antenna approximately as long as body (Miyazaki 1971;Heie 1995). Morphological identification keys and original descriptions of Megoura spp. (Miyazaki 1971;Heie 1995;Lee et al. 2002;Eastop 2011) suggest that this species is referable to M. crassicauda in Japan. However, the apterous viviparous female of this species is distinguished from M. crassicauda by antennal segment III with 40-59 secondary rhinaria, abdominal tergite III with 11-13 setae, pale tibia (except distal 1/9 dark), and pale yellow cauda.
The present paper describes this new species, and provides a revised key to species of Megoura of the world.

Materials and methods
Aphid samples for this study were collected in 2012 on Lathyrus japonicus subsp. japonicus in Japan. Each sample of aphid colonies was preserved in 80% alcohol, and mounted specimens were prepared in Canada balsam, following methods by Blackman and Eastop (2000). Illustrations for each species were taken by digital camera, Carl Zeiss, AxioCam MRc5 attached on the microscope, Carl Zeiss Microimaging GmbH 37801, Gottingen, Germany. Measurements for each specimen are taken from the digital images by the software, Axio Vision Re. 4.8.

Megoura lathyricola
Etymology. The specific epithet is composed of the root of the plant genus (lathyr) and the lexeme "col" that, in this case, means 'living on'.
Apterous viviparous female. (Figs 1A-H, 2A) Color alive: Head yellowish brown with antennae dark brown, thorax and abdomen pale green. Legs pale yellowish brown except distal 1/9 of tibiae including tarsi dark brown. SIPH dark brown. Cauda pale. Color of macerated specimens: Head yellowish brown and antennae dark brown. Rostrum pale, except the tip of URS dark brown. Thorax yellowish brown and abdomen entirely pale. Legs pale except distal 1/9 of tibiae and tarsi dark brown. SIPH dark brown and cauda pale except extreme end. Morphology: Body spindle shaped. Head: smooth on ventrum and dorsum including three pairs of acuminate setae. Antennal tubercle well developed with 3-5 setae on both side, frons U-shaped with four setae on vertex, including weakly developed median tubercle. Ant.I smooth; Ant.II granulate; Ant.III weakly imbricate with short setae, bearing 40-59 secondary rhinaria irregularly spaced; Ant.IV imbricate with 12-18 setae with no secondary rhinaria; Ant.V imbricate with 8-13 setae, primary rhinarium ciliate, longest diameter of which is shorter (0.63-0.83 times) than middle width; Ant.VI imbricate with 3-7 short setae on Ant.VIb. Rostrum attaining posterior margin of mesocoxa; mandibular laminae with 4-6 setae on each side; URS longest seta 0.78-1.00 times as long as apical primary ones. Thorax: pronotum smooth with two spinal setae and one marginal seta on anterior margin. Hind coxa weakly spinulose with 6-7 acuminate setae; hind trochanter wide at base, 1.63-1.65 times as long as apical width, bearing three setae; hind femur smooth on basal 1/17, spinulose on apical 16/17 ventrally, bearing short setae, longest seta 0.43-0.48 times as long as basal width of segment; hind tibia smooth, longest seta 0.80-1.07 times as long as middle width of segment; first segment of each tarsus smooth with three setae at apex; 2HT imbricate with 10-11 setae. Abdomen: dorsum smooth, membranous with 11-13 setae on tergite III, 0.37-0.47 times as long as basal width of hind femur. SIPH swollen, weakly spinulose except smooth base, irregularly reticulated on distal end, apex flanged. Cauda elongate, triangular, ventral spinules strong and dense, in groups of one or two; dorsal ornamentation composed of ribbed imbrication.
Distribution and host-plant. So far collected and observed only on Lathyrus japonicus subsp. japonicus in Muroran, Hokkaido and Nagasaki, Japan. This plant is distributed only in seashore areas.