Rhinusa tetra ( Fabricius, 1792 )

Caldara, Roberto, Casalini, Roberto & Baviera, Cosimo, 2012, Taxonomic and nomenclatural notes on the Rhinusa tetra (Fabricius) species complex (Coleoptera: Curculionidae), Zootaxa 3329, pp. 31-40 : 36

Rhinusa tetra ( Fabricius, 1792)

Cionus amictus Germar, 1821

Gymnetron hispidum Brullé, 1832

Gymnetron eoum Rosenschoeld, 1838 (syn. n.) Gymnetron plagiellum Gyllenhal, 1838

Gymnetron fuscescens Rosenschoeld, 1838 Gymnetron trigonale Gyllenhal, 1838

Cleopus verbasci Dufour, 1843 (syn. n.) Cleopus uncinatus Dufour, 1843 (syn. n.) Gymnetron haemorrhoum Rosenhauer, 1847 Gymnetron tetrum subrotundatum Reitter, 1907

Remarks. This is one of the commonest and most widespread species in the genus Rhinusa . In the southern part of its area of distribution it can be confused with two other very similar species, R. verbasci and R. moroderi . It can be separated from these only by the shape of the female rostrum, most easily in lateral view. Unfortunately the males of these three species differ only by average length of rostrum and aedeagus (see key to the species). It is well known that adults of R. tetra vary greatly in size (from 2.0 mm to 4.5 mm) even in specimens collected on the same plant. Since this species is oligophagous, with larvae feeding in seeds of different species of Verbascum , it is possible that the size of the specimens is influenced by the different size of the seeds in various species of Verbascum as already speculated by Peyerimhoff (1911). The same is probably true for the different lengths of the rostra of the female in various populations as is known to occur in several species of herbivorous “long-nosed weevils”.

Biological notes. Larva and adult were quoted as collected on various species of Verbascum . However, some of these observations possibly refer to other species closely related to R. tetra . We could verify the following plant associations: V. blattaria L., V. boerhavii L., V. creticum (L.) Cav., V. lychnitis L., V. n i g r u m L., V. phlomoides L., V. phoeniceum L., V. pulverulentum Vill. , V. speciosum Schrader , V. thapsiforme Schrader , V. thapsus L. Sometimes adult R. tetra were collected also on Scrophularia ( S. auriculata L., S. canina L.).

Distribution. Europe, Siberia, North Africa, Middle East, central Asia, northern India (R. Caldara, pers. data). Introduced in North America ( O'Brien & Wibmer 1982), where it was proposed as a potential candidate for the biological control of invasive Common Mullein, Verbascum thapsus L. (see Anonymous 2011).