Ctonoxylon methneri Eggers, 1922

Jordal, Bjarte H., 2024, An integrated taxonomic revision of Ctonoxylon (Coleoptera, Curculionidae, Scolytinae) reveals new Malagasy species originating from multiple recent colonisations of the island, ZooKeys 1203, pp. 95-130 : 95-130

Ctonoxylon methneri Eggers

Figs 67 , 70 , 73

Ctonoxylon methneri Eggers, 1922: 170.

Ctonoxylon griseum Schedl, 1941: 389 , syn. nov.

Ctonoxylon hamatum Schedl, 1941: 400 , syn. nov.

Type material.

Holotype (‘ type’): [ Tanzania] Udzungwa-Berge 1300–1600 m., 26. XI. 1912, Methner, coll. [ ZMHB, not found] . Holotype of C. hamatum male: [ Kenya] Nairobi [ NHMW] . Holotype of C. griseum , female: [ Kenya] Brit. O. Africa, Kikuyu [- 1.27, 36.68], E. Thomas [ NHMW] .

Diagnosis.

Length 2.3–4.2 mm. 2.1–2.3 × as long as broad; colour dark brown, dorsal setae variegated. Male frons flat, smooth, impunctate and glabrous within a triangular pattern of short setae near eyes and epistoma; female frons finely granulated with short setae; eye parts separated by almost the size of upper half; anterior lateral margin of prothorax with elongated groove near front of coxa; propleural pit present just above coxa; scutellar shield detached from elytra; elytral suture slightly buckled at midlength; apex emarginated; interstrial vestiture consisting of confused rows of variegated scale-like setae of similar length and colour as the ground vestiture.

Distribution.

Kenya, Tanzania, South Africa.

New records.

South Africa, E. Cape Prov., Katberg [GIS: - 32.479, 26.673], 01. 11. 1933, R. E. Turner, leg. [2, NHMUK] ; W. Cape province, Knysna, Diepwalle [GIS: - 33.957, 23.152], 7. 11. 2006, ex Olea capensis trunk, B. Jordal, leg ; same data except Goudveld, Krisjan Se-Nek [GIS: - 33.913, 22.948], 5. 11. 2006 ; Goudveld, Woodcutters [GIS: - 33.927, 22.976], 4. 11. 2006 ; Gouna, Grootdrai [GIS: - 33.946, 23.054], 6. 11. 2006 ; Nature’s Valley [GIS: - 33.965, 23.562], 8. 11. 2006 ; Tsitsikamma, Goesa walk [GIS: - 33.983, 23.887], 12. 11. 2006 ; Tsitsikamma, Platboos walk [GIS: - 33.980, 23.910], 14. 11. 2006 [all in ZMUB] ; Kenya, Ngong Forestry [- 1.31, 36.73], 12. 01. 1968, Malaise trap, Krombein & Spangler leg. [1, USNM] .

Biology.

This species is exclusively associated with black ironwood, Olea capensis ( Oleaceae ) where it is usually present whenever branches and trees are down. Recent field studies in the Knysna forests in the Cape region indicated no particular preference for breeding material size, ranging from 2 - cm thick branches to the largest tree trunks of> 60 cm diameter. It breeds in the same host tree as Lanurgus jubatus Jordal, 2021 , and Lanurgus xylographus Schedl, 1961 , but even though it is found in the same forest localities, C. methneri only co-occurred with these species in the same tree one out of ten collecting events. Brood size was not smaller in the thinnest branches examined and broods with larvae or older stages ranged from 17–48 (Table 5 ). Very few broods with larvae had a male parent present with the female, and then only at very early larval stage. In the large majority of dissected broods, the male left before all eggs were laid or hatched. The female left her offspring before pupal stage. Egg tunnels were always cut transversely to the wood grain and eggs deposited vertically in deep pits packed with frass.

Remarks.

Some specimens of C. methneri differ from those of C. hamatum by having slightly shorter setae on interstriae 1 and 2 but this appears to be intraspecific variation. The differences in frons and pronotum between the types of C. hamatum and C. methneri on one side, and C. griseum , is due to sexual dimorphism otherwise typical for the genus.

Figures

Figures 66–74. Dorsal, lateral, and front views of 66, 69, 72 Ctonoxylon quadrispinum female holotype 67, 70, 73 Ctonoxylon methneri male, and 68, 71, 74 Ctonoxylon atrum female holotype.