日本産コガネグモ科の検討(2)
II Cyrtophora 属
1958 年 16 巻 1 号 p. 10-17
詳細
1958 年 16 巻 1 号 p. 10-17
No Cyrtophora spider has been recorded till now in Japan. However, according to the writer's examinations, it was found that two species of Cyrtophora actually exist.
1. Cyrtophora ikomosanensis (BOESENBERG et STRAND) 1906
This species was first desdribed as Aranea ikomosnensis by BOESENBERG and STRAND. But it should be undoubtedly Cyrtophora, and has many resemblances to Cyrtophora moluccensis (Dol.) in shape and colour. The web making habit is also similar to the latter, i.e. it makes a large dome-web, about 30-80cm in dia-meter, consisting of many small wide meshes (1.5mm×2mm), which can be con-sidered as a modification of an orb-web. But the spirals have not sticky drops. The radial threads increase towards the edge, so all the meshes are of same size. This web resembles to Linyphiid web at a glance, but in the structure, this is rather nearer to Nephila than to Linyphia.
2. Cyrtophora exanthematica (DOLESCHALL) 1859
This species hitherto been known as Cyclosa bifurcata Kishida (not Walck.) in Japan. But this is not Cyclosa, and its name should be rejected as a secondary homonym on account of existence of Cyrtophora bifurcata (WALCI ENAER) 1841. The writer has identified this species with Cyrtophora exanthematica. Abdomen narrow behind and bifurcated posteriorly. Anterior part of abdomen with weak humps projecting laterally at both sides. Dorsal surface with 6 pairs of muscle-impressions and many small granules scattered exanthematically as its name shows. Two white lines run from shoulder humps to the posterior bifurcated lobes. (no granules seen in male). The web is horizontal and consists of small meshes, like Cyrtophora ikomosanensis, and irregular webs are seen above and below the main web. The spirals are not sticky like the preceding species.
The writer recognized the following two types in this genus of Japan.
Group I (Euetria type)
1. MOA square, both sides almost parallel. 2. Legs long, patella plus tibia shorter than metatarsus plus tarsus. 3. Posterior eye row almost straight, 4. Pro-tuberances on anterior part of abdomen conical. 5. Web is dome-shaped.
Cyrtophòra ikomosanensis belongs to this group.
Group II (Cyrtophora type)
1. MOA trapezoid, wider in font than behind. 2. Legs snort and stout, patella plus tibia longer than metatarsus plus tarsus 3. Posterior eye row strongly recu-rved. 4. Pretuberances on abdomen poined laterally. 5. Web is horizontal. Cyrtophora exanthematica belongs to this group.
