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Suffolk Natural History, Vol. 39
SUFFOLK GRASSLAND AS A BUTTERFLY HABITAT ROB PARKER Grasses (Poaceae) provide the larval food of almost a third of British butterflies, and of 10 of those breeding in Suffolk. All the butterflies concerned are brown in colour, and they belong to the families Satyridae (the Browns) and Hesperiidae (the Skippers). Yet individual species are selective; not every grass will do. Established records of which larvae will eat which species of grass are not always dependable. Some are too generalised, some record grasses accepted in captivity which would not have been chosen in the wild, the worst could be based on observations made years ago, possibly in a foreign land, and perpetuated without confirmation. Given the loss of grassland in Suffolk, and the changing distribution of some of the butterfly species, it seems worth matching butterflies to specific grass species, if only to see whether any pattern emerges in host plant exploitation. The Semantics of Larval Host Plants (LHPs) The plant eaten by larvae may properly be described as the Larval Host Plant, and abbreviated to LHP. Although most popular entomological textbooks use the convenient expression “foodplant”, no such word is to be found in dictionaries or in biological encyclopaedia, though foodstuff generally is listed. Pabulum is Latin for food, and is also in regular use by some entomologists to mean the food of caterpillars. This paper nonetheless follows Asher et al., (2001) in using the familiar “foodplant”. Grass Species Simpson (1982) lists some 139 grasses found in Suffolk, a 100 of which are native species. Many of these have more than one vernacular name, not all of which are helpful in identification. Some are common, and are considered to be palatable to the caterpillars of many butterfly species (Bink, 1985), whereas others are scarce or local, yet favoured by certain butterflies. Only 32 of these grasses are noted in the entomological literature as foodplants of any of the 10 butterfly species. Typically, matches will occur where a particular biotope hosting a particular grass community also suits a particular butterfly. For example, Graylings are found on the sandy soils of the Sandlings and on the coast, where Marram grows and serves as one of several foodplants for the butterfly. Marram has not been recorded as the foodplant of any of the other 9 butterflies. On the other hand, Cock’s-foot suits 8 different butterfly species, and Yorkshire-fog suits 5. It is certain that many entomologists recognise Cock’s-foot and Yorkshire-fog, but are unfamiliar with more obscure grasses, so there is an inevitable recorder bias. Table 1 below lists only the 32 grass species that have attracted records. They are presented in the same sequence used by Simpson (1982), but updated with the scientific and vernacular names used in New Flora of the British Isles (Stace, 1997). Sedges are not grasses, and have not been included, even though the Ringlet caterpillar has been known to eat Wood-sedge and other Carex species. Grass species not found in Suffolk have been excluded, even those known to suit some butterflies found in the county.
Trans. Suffolk Nat. Soc. 39 (2003)