Rhopalosiphum chusqueae Pérez Hidalgo & Villalobos Muller 2012

Chusquea tomentosa (Poaceae, Bambusoideae) is the only known host of Rhopalosiphum chusqueae. This bamboo is endemic to the country and can be found in several areas of the Cordillera de Talamanca at an altitude of between 2450 and 3000 m (Widmer 1997; Hammel et al. 2003). Species of Chusquea (approximately 120 described) can be found at between 800 and 3800 m in dry and humid forests from Mexico to Chile and Argentina (Clark 1989). As species in the genus Rhopalosiphum are not strictly stenophagous, Rhopalosiphum chusqueae may also live on other species of Chusquea, or even on other bamboos and live in other parts of America. On the plant, the aphids live close to the nodes well protected by the leaves (Figs 1C, 1D) and not easily detectable, as shown by fruitless efforts to locate other colonies. So far, only one aphid species had been recorded on Chusquea: Hysteroneura setariae (Thomas) on Chusquea abietifolia Griseb, in Cuba (Holman 1974). Blackman and Eastop (1994) present two identification keys to the aphid species living on Arundinaria and on Bambusa, genera that include arboreal bamboos; several of these aphid species belong to the subfamily Aphidinae. Blackman and Eastop (2006) report the presence of aphid species on several genera of non-arboreal bamboos such as Chusquea, Pseudosasa, Sinoarundinaria, Thamnocalamus, Thysanolaena, and also Arundinaria (other bamboo genera are included but no Aphidinae species have been recorded on them), and for the identification of these species the reader is forwarded to the “keys [of 1994] to aphids on Arundinaria and Bambusa”, or to the “keys [of 2006] to apterae on Digitaria and other genera of herbaceous Poaceae”. To make the identification work easier, it seems useful to present one compendium-key to the identification of apterous viviparous females of Aphidinae species recorded on species of Bambusoideae in the World. This key has been prepared using the general structure and several couplets in all of those keys by Blackman and Eastop; thirteen Aphidinae species and subspecies have been included, and are: Hysteroneura setariae (Thomas, 1878), Melanaphis arundinariae (Takahashi, 1937), Melanaphis bambusae (Fullaway, 1910), Melanaphis meghalayensis bengalensis Raychaudhuri [D.N.] and Banerjee [C.], 1974, Melanaphis meghalayensis meghalayensis Raychaudhuri [D.N.] and Banerjee [C.], 1974, Melanaphis pahanensis (Takahashi, 1950), Melanaphis sacchari (Zehntner, 1897), Rhopalosiphum arundinariae (Tissot, 1933) and Rhopalosiphum rufiabdominale (Schrank, 1899) (Aphidinae Aphidini Rhopalosiphina), and Sitobion bambusicola (Ghosh [L.K.], 1986), Sitobion fragariae (Walker, 1848), Sitobion miscanthi (Takahashi, 1921) and Sitobion papillatum subnudum Remaudière, 1985 (Aphidinae Macrosiphini). 1 Siphunculus without apical zone of polygonal reticulation. Abdominal segments I and VII with marginal tubercles (papillae) placed dorsally to the respective spiracular apertures. Cuticle of dorsum of the abdomen membranous, a sclerotized patch absent 2 – Siphunculus with apical zone of polygonal reticulation (at least two rows of cells). Abdominal segments I and VII usually without marginal tubercles (papillae), but if they are present then spinal papillae present on head and several abdominal segments. Dorsum of the abdomen with a sclerotized patch more or less extended and pigmented 12 2 Aphids spindle-shaped, green when alive. Siphunculus very small (less than 0.7 times cauda), thin, cylindrical and narrow-based, flangeless, and with not functional aperture Hyalopterus pruni [and other Hyalopterus spp.] – Aphids broad oval-shaped. Siphunculus 0.5–2.5 times cauda (if less than 0.6 times then less than 2 times longer than its basal width), shaped differently and with functional aperture 3 3 Siphunculus short, usually thick or rather thick, less than (often much less than) 2.4 times longer than its basal width, 0.4–1.2 times cauda, and usually with a well-developed, rather swollen flange 4 – Siphunculus usually longer than cauda (if less than 1.2 times cauda then it is more than 2.4 times its basal width and/or has a small flange), tapering, cylindrical or swollen 9 4 Setae on antennal segment III at most 1.5 times the basal diameter of the segment. [Alatae viviparous females with wing veins dark bordered] 5 – Setae on antennal segment III at least 2.0 times the basal diameter of the segment. [Alatae viviparous females with wing veins not dark bordered] 6 5 Cauda with only 4-6 setae. Coxae dark Melanaphis bambusae – Cauda with 7-20 setae. Coxae pale Melanaphis sacchari 6 Antennae five-segmented. Siphunculus 1.5 times its basal width at least Melanaphis arundinariae – Antennae six-segmented. Siphunculus 1.4 times its basal width at most 7 7 Siphunculus 1.1–1.4 times its basal width. Terminal processus of antennal segment VI at most 2.3 times the base Melanaphis pahanensis – Siphunculus 0.8–0.9 times its basal width. Terminal processus of antennal segment VI at least 2.2 times the base [Melanaphis meghalayensis] 8 8 Cauda with 4–6 setae and anterior half of the genital plate with 4–7 setae Melanaphis meghalayensis meghalayensis – Cauda with 7–10 setae and anterior half of the genital plate with 2 setae Melanaphis meghalayensis bengalensis 9 Setae on antennal segment III shorter than the basal width of the segment 10 – Setae on antennal segment III longer than the basal width of the segment 11 10 Cauda at least 1.5 times its basal width, finger-shaped, with basal constriction, paler than cauda, and usually with 4 setae. [Alate viviparous females with only one oblique vein in hindwing] Hysteroneura setariae – Cauda a little longer that its basal width, cone-shaped, without basal constriction, as dark as siphunculi, and with approximately 8 setae. [Alate viviparous females with two oblique veins in hindwing] Rhopalosiphum arundinariae 11 Antennae usually five-segmented. Setae on antennal segment III 3.0–5.0 times the basal width of the segment. Abdominal segment VIII with 3–8 setae. Ultimate rostral segment 1.3–1.8 times second segment of the hind tarsus. Terminal processus of antennal segment VI 4.0–6.5 times the base Rhopalosiphum rufiabdominale – Antennae six-segmented. Setae on antennal segment III 1.8–2.6 times the basal width of the segment. Abdominal segment VIII with 4 setae. Terminal processus of antennal segment VI 3.9-–4.4 times the base Rhopalosiphum chusqueae sp. n. 12 Spinal tubercles (papillae) present on the head and abdominal segments (V)VI-VIII; marginal ones present on prothorax and abdominal segments (I)II–V and infrequently on VII Sitobion papillatum subnudum – Spinal tubercles (papillae) absent; marginal ones on abdominal segment II–V usually absent, and always absent on abdominal segments I and VII 13 13 Cauda dusky (but not as dark as siphunculi) and with a rather pointed apex. Siphunculus 2.0–2.1 times cauda. Aphids yellowish when alive Sitobion bambusicola – Cauda pale (very contrasted with siphunculi) with a variably shaped apex. Siphunculus 1.4–2.7 times cauda. Aphids variable in colour when alive 14 14 Siphunculi 1.75–2.25 times cauda, which has a rather rounded apex Sitobion fragariae – Siphunculi 1.4–1.9 times cauda, which has a rather pointed apex Sitobion miscanthi