BR. J. ENT. NAT. HIST., 7: 1994 



THE CURRENT STATUS OF THE LESSER MOTTLED 



GRASSHOPPER, STENOBOTHRUS STIGMATKl S 



(RAMBUR) ON THE ISLE OF MAN 



Andrew Cherrill 



Department of Agricultural and Environmental Science, University of Newcastle upon Tyne, 

 Porter Building, St Thomas Street, Newcastle upon Tyne NE1 7RU. 



The discovery of the lesser mottled grasshopper, Stenobothrus stigmaticus 

 (Rambur), on the Isle of Man in 1962 was a surprise (Ragge, 1963). Although present 

 in Northern France, the Low Countries and Scandinavia, the grasshopper has not 

 been recorded from any other site in the British Isles. The mystery of the origin of 

 the population on the Isle of Man is discussed by Ragge (1963, 1965) and Burton 

 (1965, 1990). A more immediate practical concern, however, is the lack of quantitative 

 information on the grasshopper's habitat requirements on the island. In 1990, 

 a proposal to extend an existing golf course over much of the grasshopper's site 

 highlighted the importance of such basic data. In late July of that year I visited the 

 island to assess the situation at first hand (Cherrill, 1990), returning in early August 

 1993 to review subsequent developments. This article reports on these field visits and 

 makes tentative suggestions for the species' conservation. 



Identification of S. Stigmaticus 



S. stigmaticus is an inconspicuous green grasshopper, with brownish wings. The 

 most obvious characteristics separating it from other members of the British fauna 

 are its small size and the presence of a tooth on each valve of the ovipositor in females 

 (Ragge, 1965; Marshall & Haes, 1988). In the British Isles, the latter characteristic 

 is shared only by females of Stenobothrus lineatus (Panz.) which measure 17-23 mm 

 in length, compared to a length of 12-15 mm for adult females of S. stigmaticus. 

 The dimensions of a number of grasshopper specimens collected by the author on 

 the Isle of Man in July 1990 are shown in Table 1 . Although the numbers of specimens 

 of each species are low, it is evident that the small overall size of S. stigmaticus can 

 be attributed largely to its relatively short wings. Along other dimensions, S. 

 stigmaticus is as large or larger than co-occurring specimens of Myrmeleotcttix 

 maculatus (Thunb.). Both species are considerably smaller than the common field 

 grasshopper, Chorthippus brunneus (Thunb.). 



Distribution 



On the Isle of Man, the grasshopper occurs solely on and in the vicinity of the 

 Langness Peninsula which forms the South Eastern tip of the island. The peninsula. 

 which is approximately 2.5 km long and 0.5 km wide, supports a number of historical 

 landmarks including the Sea Mark (usually called the Herring Tower), the Powder 

 House, ancient earthworks and a working lighthouse (Fig. 1). With the exception 

 of a raised beach and small areas of sand-dune and salt-marsh on its western side. 

 the peninsula's shore-line is steeply rocky. The peninsula is renowed for its aesthetic 

 appeal and is an important site for breeding birds. The peninsula lies within an 

 ornithological reserve, but otherwise neither the peninsula nor the grasshopper 

 currently enjoys special protection under Manx law. 



The landward half of the peninsula is dominated by a golf course on sand-dunes 

 and blown sand. The seaward portion supports substantial outcrops of slate. 



