The distribution and biology of Bittacus tjederi Londt, 1970 (Mecoptera: Bittacidae)

Abstract

Bittacus tjederi Londt, 1970, together with B. capensis (Thunberg, 1784), B. smithersi Londt, 1972, and B. milleri Londt, 1978, constitute a distinctive species-group of hangingflies which is distributed between Grahamstown and Citrusdal in the southern parts of South Africa (Londt 1978). The recent capture of some B. tjederi specimens prompts this short report. Londt described B. tjederi from a relatively long series collected by a South African Museum expedition (Londt 1970), and later added a second record (Londt 1972). Londt (1978), in describing B. milleri, briefly discussed the interesting distribution of this species-group. A list of all known specimens of B. tjederi follows – exact label data being provided (lines of information separated by the symbol ‘/ ’). The exact coordinates of previously published localities are not known, and quarterdegree grid references are all that can safely be provided (in square brackets after the relevant place names). Published records. SOUTH AFRICA: 218 (including holotype), 169 (including allotype), ‘Goedehoop/Heidelberg [3420BB] Distr., /C.P.’, ‘Mus., Exped., /Oct. 1951’. Primary types and most of the paratypes are housed in the Iziko South African Museum, Cape Town. Two pairs of paratypes, originally stated as being in my personal collection, now form part of the Natal Museum’s collection in Pietermaritzburg (NMSA); 18, 29, ‘South Africa/Swellendam [3420AB]/14.11.1964/F. Honiball’ (18, 19 in Stellenbosch University collection, 19 in NMSA). New record: 48, 59, ‘South Africa: W Cape/Pat Busch Nature Reserve/33°46’17”S: 19°59’55”E/ 18-20.x.2005 JGH Londt / 317m Renosterbos / and rocky road verges’ (NMSA – pinned except for 18 preserved in ethanol for molecular analysis). A map of the distribution of species within the B. capensis group was published by Londt (1978). Bittacus smithersi is known only from the vicinity of Grahamstown, B. capensis has a wider distribution between Port Elizabeth and Knysna, B. tjederi is now known to occur between Heidelberg and Robertson, and finally B. milleri is found between Citrusdal and Clanwilliam. The species are accordingly allopatric, their combined distributions extending as a narrow band across the southern tip of South Africa, between c. latitude 32–34°S and c. longitude 19–27°E. Far more data are needed before it will be possible to establish the exact limits of each species so that the factors responsible for maintaining their separation can be understood. As far as B. tjederi is concerned, the new locality is of special interest as it is situated on the southern slopes of the Langeberg mountain range. While the exact coordinates of the collection sites involved in the ‘Goedehoop’ and ‘Swellendam’ material are not known, both centres (i.e. Heidelberg and Swellendam) also lie south of the Langeberg and within 15 km of the mountains. It is tempting to suggest that all three collecting localities probably lie in the southern foothills of the Langeberg which are relatively cooler and better vegetated than surrounding areas. This extensive mountain range effectively separates the Cape Floristic Region to the south from the Succulent Karoo Region to the north. It is possible that B. tjederi is confined to a relatively narrow area along the northern boundary of the Cape Floristic Region, well known internationally for its rich floral diversity (Van Wyk & Smith 2001). The Cape Floristic Region receives winter rainfall, while the more arid Succulent Karoo receives low summer rainfall. Bittacus tjederi, like the other species in the B. capensis group, has been collected mainly during October and November. This relatively short period of adult activity coincides with the end of the local rainy season and the beginning of warmer summer weather. Without exception, all the Pat Busch Nature Reserve specimens of B. tjederi were found hanging from the twigs of a group of bushes, identified as Ortholobium candicans (Eckl. & Zeyh.) C.H. Stirt, found growing along the verges of a sandy farm road (Fig. 1). These plants reach a height of about 2 m and have small c. 15 mm long, narrow, trifoliolate leaves borne on rather straight branches (Fig. 2). The c. 10 mm wide creamy white flowers were much in evidence at the time of the collec-