Colopha setaricola, Sano & Akimoto, 2005

Sano, Masakazu & Akimoto, Shin-Ichi, 2005, Distribution of bisexual and unisexual species in the aphid genus Colopha Monell (Aphididae: Eriosomatinae), with the description of a new species in Japan, Journal of Natural History 39 (4), pp. 337-349 : 338-344

Colopha setaricola sp. nov.

Measurements are indicated as ranges and means (in parentheses), based on five individuals from each of the three localities. Drawings are based on materials from one locality, from which the holotype was collected. The holotype and some paratypes are deposited in Systematic Entomology, Hokkaido University, Sapporo, Japan and other paratypes in the National Science Museum, Tokyo, Japan; Departamento de Biología Animal, Universidad de León, León, Spain; and the Natural History Museum, London, UK.

First instar exule

Body ( Figures 1, 2 ) elliptical, 0.64–0.75 (0.70) mm long, 0.37–0.41 (0.40) times as wide as long, with distinct wax gland plates and sclerotized bands scattered over.

Eyes with three ommatidia and, in the space surrounded by them, with about 15 small sclerotized tubercles. Antennae ( Figure 3 ) five-segmented, 0.145 –0.170 (0.157) mm long, 0.20–0.24 (0.22) times as long as body, 1.02–1.21 (1.13) times the length of hind femorotrochanter. Antennal segments I–III smooth, segments IV and V spinulose. Antennal setae sparse; setal arrangement on each segment as follows: I 3 (one of which is feeble), II 2, III 0, IV 4, and V 2 + 5. Primary rhinarium surrounded by cilia in a single row, with a circular opening, from which a semi-transparent tonguelet projects. Tonguelet on segment IV small and furcated, that on segment V extending apically like a horn. Some accessory rhinaria present close to primary one, surrounded by cilia in a single row, without a tonguelet. Rostrum reaching abdominal segment IV or V. Ultimate segment ( Figure 4 ) spinulose, with two pairs of accessory setae, 0.075–0.88 (0.82) mm long, 0.55–0.63 (0.59) times the length of hind femorotrochanter.

Femorotrochanter slender, slightly spinulose along hind margin, 0.129 –0.145 (0.139) mm long in hind legs. Tibia shorter than femorotrochanter, spinulose, 0.105 – 0.121 (0.116) mm long in hind legs. Tarsus ( Figure 5 ) spinulose, with six pairs of setae; two pairs dorsally, two pairs ventrally, one pair laterally, and one pair on empodium. In fore legs one of the two dorso-apical setae capitate and longer, but in middle and hind legs the two setae capitate and equal in length. Empodial setae simple, exceeding the point of claws. Hind claws 0.022 –0.026 (0.024) mm long, 0.43–0.51 (0.48) times tarsal length.

Wax gland plates ( Figure 6 ) circular or elliptical, consisting of one or two central fields and circumferential cells. Central field microscopically bright, with a broad blackish rim, usually larger than circumferential cells. Circumferential cells with minute blackish points scattered over, surrounding the central field(s) in a single layer. Head ( Figures 1, 2 ) with five pairs of wax gland plates; on the dorsum one pair medio-posteriorly and one pair latero-posteriorly; on the frons one pair; on the ventrum one pair medio-anteriorly and one pair latero-facially. Prothorax with one dorso-spinal pair of wax gland plate and one ventrolateral pair. Meso- and metathorax and abdominal segments I–VI each with three pairs at dorso-spinal, dorso-pleural and ventro-lateral positions. Abdominal segment VII with one dorso-lateral and one ventro-lateral pairs. Lateral pair rather located on the dorsal side on anterior segments, especially on thorax.

Body setae all simple and short. Head ( Figures 1, 2 ) with eight pairs of setae; on the dorsum one pair outside medio-posterior wax gland plates, one pair outside latero-posterior wax gland plates, one pair laterally just above antennal bases, and one pair medioanteriorly; on the frons one pair; on the ventrum three pairs facially. Pronotum with two spinal pairs of setae and two lateral pairs. Meso- and metanotum each with one spinal, one pleural and two lateral pairs. Abdominal tergites I–VI each with three pairs at spinal, pleural and lateral positions. Abdominal tergite VII with one spinal and one lateral pair. Abdominal tergite VIII with one pleural pair. Cauda with two setae. Abdominal sternite VIII with four setae.

Abdominal segments I–VI each with one pair of sclerotized bands, on which spinal and pleural setae, and spinal and pleural wax gland plates are situated. Abdominal segments VII and VIII sclerotized dorsally.

Adult exule

Body elliptical, tapering posteriorly, 1.42–1.93 (1.69) mm long, 0.60–0.79 (0.69) times as wide as long, with distinct wax gland plates scattered over.

Eyes with about 10 ommatidia, without small sclerotized tubercles in the space surrounded by them. Arrangement of cephalic setae and wax gland plates ( Figure 7 ) as in the first instar exule, but some wax gland plates rudimentary or absent. Rostrum short, reaching a little beyond fore coxae. Antennae ( Figure 8 ) six-segmented with the division between segments III and IV sometimes incomplete, or rarely five-segmented with segment III completely fused with IV, 0.198 –0.251 (0.223) mm long, 0.12–0.16 (0.13) times as long as body, 0.89–1.15 (0.98) times the length of hind femorotrochanter. Primary rhinarium not transversely extended, surrounded by cilia in a single row, with a circular opening, from which a semi-transparent tonguelet projects. Some accessory rhinaria present on segment VI. Antennal setae short and scarce; their arrangement as follows, I 2–3 (one of which is feeble), II 2, III 0–1, IV 0, V 4, and VI 2+425. Ultimate segment ( Figure 9 ) slightly spinulose, 0.070 –0.093 (0.081) mm long, 0.32–0.38 (0.35) times as long as hind femorotrochanter, with two pairs of accessory setae.

Femorotrochanter tapering apically, slightly spinulose along posterior margin, 0.198 – 0.250 (0.229) mm long in hind legs. Tibia shorter than femorotrochanter. Fore tarsus ( Figure 10 ) short, 0.033 –0.046 (0.040) mm long, ventro-apically with a large prominent setal socket, whose seta is stout and shorter than the points of claws, about 0.015 mm long. Middle and hind tarsi ( Figure 11 ) rather long, 0.038–0.55 (0.048) mm long and 0.045 – 0.063 (0.056) mm long, respectively, without a well-developed setal socket. Arrangement of setae on tarsi as in the first instar exule, but lacking an empodial pair.

Wax gland plates ( Figure 12 ) as in the first instar exule, but central fields weakly rimmed as in circumferential cells with rough blackish points scattered over and sometimes not distinguishable from circumferential cells. Arrangement of wax gland plates as in the first instar exule. Body setae short, as long as the diameter of wax gland plates, arranged in a transverse row. Cornicles absent. Genital plate ( Figure 13 ) consisting of two lobes, altogether with 10–17 setae, two of which are much stouter and longer and situated at the centre of each lobe. Anal plate ( Figure 13 ) with slightly lifting three lobes, with 11–18 setae and 5–9 feeble setae, the latter of which are scattered along anterior margin of a depression surrounded by three lobes. Cauda with two setae.

Sexupara

Materials from the two localities included males and bisexual females in the abdomen, suggesting that they are sexuparae, not alate exules.

Body 1.56–2.16 (1.91) mm long, without wax gland plates or sclerotized bands on abdomen.

Antennae ( Figure 14 ) six-segmented. Antennal segment III the longest, as long as segments IV, V and VI combined, 0.23–0.28 (0.25) mm long. Segment IV a little longer than segment V, but shorter than segments V and VI combined, 0.085–0.11 (0.097) mm long. Segment V a little longer than segment VI, 0.078 –0.090 (0.83) mm long. Segment VI slightly spinulose, 0.065 –0.083 (0.74) mm long. Antennal setae short, as long as basal width of segment III, arrangement of which as follows; II 2, III 1–6, IV 0–1, V 4, and VI 2+425. Secondary rhinaria microscopically represented as bright lines, present on segments III–VI. Those on segments III–V covering usually about half the circumference from the ventral side; some rhinaria much shorter. Secondary rhinarium on segment VI short and rudimentary. Primary rhinarium on segment V not ciliated, without an opening, always connected with the apical secondary rhinarium. Primary rhinarium on segment VI slightly ciliated with a semi-transparent tonguelet, often connected with the apical secondary rhinarium, which is more irregular in shape and sometimes thicker than other secondary ones. Some accessory rhinaria present dorsally on segment VI. Antennal segments III, IV, V, and VI with 12–18, 3–6, 3–5, and 1–3 secondary rhinaria, respectively. Head ( Figure 15 ) dorsally with five pairs of minute setae; one pair medio-posteriorly, one pair latero-posteriorly, one pair medio-anteriorly, one pair latero-posteriorly and one pair frontally. Rostrum short, a little exceeding fore coxae. Ultimate segment ( Figure 16 ) slender, spinulose, with three to five accessory setae, 0.088–0.11 (0.094) mm long, 0.83– 1.02 (0.90) times as long as the second segment of hind tarsus.

Hind femorotrochanter 0.41–0.49 (0.46) mm long. Second segment of tarsi with transverse rows of spinules. Empodial pair of setae simple, reaching the points of claws. Second segment of hind tarsus 0.099 –0.115 (0.105) mm long, with 10–11 setae, two of which are on empodium.

Cornicles absent. Cauda with two to six setae. Genital plate ( Figure 17 ) depressed in the middle, forming two lobes, altogether with 20–26 setae mainly scattered on lobes. Anal plate ( Figure 17 ) with 17–25 setae. Fore wings with once-branched media. Hind wings with two oblique veins.

Type materials

Holotype: one adult exule, Takao, Hachiôji , Tokyo Met., 23 November 1985, ex Setaria chondrachne (on the aerial parts), S. Takagi leg. Paratypes: 26 first instar exules, eight adult exules and 10 sexuparae, same data as in holotype; 22 first instar exules, 13 adult exules and 24 sexuparae, Fukiage-gyoen, the Imperial Palace , Tokyo Met., 7 November 2001, ex S. chondrachne (on the lamina), Y. Matsumoto leg ; 12 first instar exules and six adult exules, Morito-gawa River, Hayama , Kanagawa Pref., 10 November 2002, ex S. chondrachne (on the spike and under the leaf), M. Sano leg.

Distribution

Japan (central Honshû).

Host plant

Setaria chondrachne (Poaceae) . This species forms colonies on the aerial parts of the secondary host, and the colonies are densely covered with a large amount of wax ( Figure 18 ). Primary host plant unknown.

Remarks

Adult exules of C. setaricola can be distinguished from those of other Colopha species in the antennae, eyes and wax gland plates. C. setaricola has usually six-segmented antennae, while other species have four- or five-segmented antennae. C. setaricola has eyes consisting of about 10 ommatidia, while other species have only three ommatidia. In C. setaricola the wax gland plates have a central field that is weakly rimmed as in circumferential cells, while in other Colopha species wax gland plates have a conspicuously rimmed central field.

First instar exules of C. setaricola can be distinguished from those of C. kansugei , the only species described for this stage, by the abdomen, tarsi and ultimate rostral segment; C. setaricola has sclerotized bands on abdominal tergites I–VII, while C. kansugei has abdomen not sclerotized; the ultimate rostral segment of C. setaricola is densely spinulose, while that of C. kansugei is very slightly spinulose; C. setaricola has symmetrical claws and symmetrical dorso-apical setae on middle and hind tarsi, while C. kansugei has asymmetrical claws and asymmetrical dorso-apical setae on middle and hind tarsi.

Life cycle

It is likely that this species reproduces parthenogenetically on the secondary host plants, although sexuparae are produced in autumn. No alate exules have been found. Despite our extensive survey and a long history of galling aphid studies in Japan ( Matsumura 1917; Monzen 1929; Shinji 1941, 1944; Yukawa and Masuda 1996), no galls of Colopha species have been found on Ulmus spp. or Zelkova serrata .

Figures

Figure 18. A colony of Colopha setaricola on Setaria chondrachne. (Photographed in Fukiage-gyoen, the Imperial Palace, Tokyo, Japan; courtesy of Y. Matsumoto.)

Figures 1–6. First instar exule of C. setaricola. (1) Body in dorsal view. (2) Body in ventral view. (3) Antenna in ventral view. (4) Ultimate rostral segment. (5) Hind tarsus. (6) Wax gland plate on pleural position of abdominal tergite IV. Scale bar: 0.2 mm (1, 2); 0.1 mm (3); 0.05 mm (4–6).

Figures 7–13. Adult exule of C. setaricola. (7) Antenna in ventral view. (8) Head in dorsal view. (9) Ultimate rostral segment. (10). Fore tarsus in posterior view. (11) Hind tarsus. (12) Wax gland plates. (13) Genital and anal plates. Scale bar: 0.2 mm (8, 13); 0.1 mm (7, 12); 0.05 mm (9–11).

Figures 14–17. Sexupara of C. setaricola. (14) Antenna in ventral view. (15) Head in dorsal view. (16) Ultimate rostral segment. (17) Genital and anal plates. Scale bar: 0.2 mm (14, 15, 17); 0.1 mm (16).