Habitat preferences of three Chorthippus species (Orthoptera: Acrididae) in the Chelmsford area
areas, provided that the sward is not too short or too tall. This species is perhaps benefiting from
the increased provision of grassland areas on agricultural land which may facilitate its dispersal to
new inland habitats.
All three Chorthippus species were absent or in very low abundance in the heavily grazed Long
Meadow which was dominated by L. perenne and characterised by a very short sward. These
swards may provide limited cover from adverse weather conditions and predators, and poor qualify
food resources. In contrast, Writtle Set-aside was dominated by P. pratense that produced a very
tall sward which excluded C. albomarginatus and C. brunneus. This tall, dense sward with very
little bare earth could be considered a 'cold' grassland where the temperatures are low, which may-
delay egg development and hatching (van Wingerden et al. 1991). The absence of bare earth or
structural differentiation in such grasslands means that 'warm' basking and egg-laying sites arc not
present.
Many authors mention the importance of bare earth as egg-laying sites for grasshoppers (Choudhuri
1958). However, favourable grasshopper sites such as Mill Green Common and Galleywood
Common had very little bare earth (Table 4). Waloff (1950) states that C. parallelus has been
found to oviposit into grass covered soil, which may have allowed this species to build up large
populations at Mill Green Common.
Grasslands which were relatively unmanaged or have low intensity management regimes such as
Mill Green Common and Galleywood Common were the preferred habitats for C. brunneus and C.
parallelus. However, these grasslands were on infertile, acidic soils, where a short, sparse sward
comprised of fine-leaved grasses such as A. capillaris may be maintained without cutting because
tussock forming competitive grasses rarely invade. On more fertile soils, unmanaged grasslands
become tall and dense which appears to be highly unsuitable for grasshoppers.
Conclusion
The implications of this research for the conservation of farmland ecosystems are clear. Grasshoppers
are prey for declining farmland bird species such as Skylark Alauda arvensis and Grey Partridge
Perdix perdix. The lack of grasshoppers on agricultural land, due to flie dearth of suitable habitats
must then limit the food supply of these predators. The authors arc conducting further research
into the effects of agricultural management regimes on grasshoppers at Writtle College.
References
AUSDEN, M. (1996) Invertebrates. In: Sutherland. W.J. (ed.) Ecological census techniques: a handbook.
Cambridge University Press. Cambridge. Pp.139-177.
BERNAYS, E.A. & CHAPMAN, R.F. (1970a) Experiments to determine the basis of food selection by
Chorthippus parallelus (Zetterstedt) (Orthoptera: Acrididae) in the field. Journal of Animal Ecology 39:
761-776.
BERNAYS, E.A. & CHAPMAN, R.F. (1970b) Food selection by Chorthippus parallelus (Zetterstedt)
(Orthoptera: Acrididae) in the field. Journal of Animal Ecology 39: 383-394
CHELMSFORD BOROUGH COUNCIL (1995) Galleywood Common, Local Nature Reserve. Chelmsford
Borough Council. Chelmsford.
CHOUDHURI, J.C.B. (1958) Experimental studies on the choice of oviposition sites by two species of
Chorthippus (Orthoptera: Acrididae). Journal of Animal Ecology 27: 201-215.
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Essex Naturalist (New Series) 20 (2003)