Tim Gardiner

Does microclimate affect grasshopper populations after cutting of hay in improved grassland

The microclimate of an improved hay meadow was studied using Tinytag dataloggers to record sward temperature after cutting. Temperatures in the sward were then compared to grasshopper abundances to see if mowing created an excessively hot microclimate unfavourable for sustained grasshopper activity in mid summer. The abundance of Chorthippus albomarginatus and Chorthippus parallelus was significantly reduced on the hay plots compared to the unmanaged control swards, which may have been due to high sward temperatures created by the absence of tall, shady vegetation in which grasshoppers may take refuge to avoid overheating. This study suggests that a combination of mortality caused by the physical process of mowing, and high sward temperatures created by removal of the standing crop by cutting may cause the low abundance of grasshoppers in improved grassland in eastern England. This research is particularly important when considering the orthopteran assemblages of Environmental Stewardship Scheme field margins where mowing for hay in July and August may seriously reduce grasshopper populations. If mowing of grassland has to occur during the grasshopper season, we suggest a later cut in September or a system of rotational mowing, leaving areas of uncut grassland as shelter.

The influence of sward height and vegetation composition in determining the habitat preferences of three Chorthippus species (Orthoptera: Acrididae) in Chelmsford, Essex, UK

Abstract This paper investigates the habitat preferences of Chorthippus albomarginatus, Chorthippus brunneus and Chorthippus parallelus in relation to sward height and vegetation composition. using 2 X 2-m quadrats, the grasshopper fauna of 15 sites was surveyed in July and August of 2000 and 2001. The results obtained highlight the importance of sward height and vegetation composition in determining grasshopper abundance. The three Chorthippus species were found to favor sward heights between 100 to 200 mm. C. brunneus and C. parallelus in particular, were positively associated with fine-leaved grass species such as Agrostis spp. or Festuca spp. (p < 0.05) and negatively associated with Lolium perenne L. and Poa trivialis L. (p < 0.01). Both C. parallelus and C. brunneus were found to be in significantly higher abundance at heathland sites than in agricultural habitats. This may have been because the farmland sites were dominated by L. perenne, which may not be a suitable food resource for grasshoppers, whereas heathland swards tended to be composed of fine-leaved grass species such as Agrostis capillaris, which might be more favorable for adult feeding. The lack of suitable swards on agricultural land may severely restrict the occurrence of these grasshopper species. This could have important conservation implications for rare farmland bird species, such as Emberiza cirlus which utilise grasshoppers as a food source.

A comparison of three sampling techniques used to estimate the population density and assemblage diversity of Orthoptera

Abstract We undertook a comparative study in 2004 at Writtle College, Chelmsford, Essex, UK, using box quadrat, open quadrat and transect sampling techniques, to ascertain the significance of emigration and immigration of individuals from survey plots during sampling and the implications for abundance estimation and subsequent calculation of assemblage diversity. Both open quadrat and transect techniques consistently produced underestimates of total Orthoptera density, Chorthippus nymph density and Chorthippus parallelus adult density, when compared to box quadrat sampling, although the differences between techniques were not statistically significant. We suggest that these underestimates of density using the former techniques were due to individuals escaping from the observer during sampling, whereas individuals jumped onto the high sides of the box quadrats. Both open quadrat and transect monitoring tended to miss the tettigoniids Metrioptera roeselii and Conocephalus discolor, leading to underestimates of species richness when compared to box quadrat sampling. We suggest that if surveyors wish to ascertain bushcricket abundance or species richness at a study site, methods that constrain movement of individuals, such as box quadrats, should be used.

Macropterism of Roesel's Bushcricket Metrioptera roeselii in Relation to Climate Change and Landscape Structure in Eastern England

Abstract There has been a considerable range expansion for Roesels bushcricket Metrioptera roeselii in Essex since 1980, and it is often assumed that the macropterous (long-winged) form (f. diluta) has played an important role. A systematic study of the occurrence and distribution of this bushcricket in the county shows that this range expansion has corresponded with a significant increase in air temperature and the availability of tall grassland on farmland, due to the introduction of set-aside and agri-environment schemes such as Countryside Stewardship. These tall grasslands are particularly important for M. roeselii in areas of the county (e.g., the northwest) where hedgerow removal has been severe since the 1940s. This study indicates that the previous years air temperature may be the most crucial climatic determinant of macroptery, hot weather leading to successful breeding and high population densities in the following year. These populations may then produce macropterous individuals in response to overcrowding; this may explain the occurrence of long-winged M. roeselii in years with cool and damp weather. However, this study fails to provide conclusive evidence of this due to a lack of quantitative macropter data. Nevertheless, a clear link is established between high temperatures and the early appearance of macropters, hot weather from April to July leading to accelerated nymphal development and earlier sightings of macropterous bushcrickets.

Agri-environment schemes and butterflies: the utilisation of two metre arable field margins

The utilisation of two metre field margins by butterflies was studied at three farms in Essex, south east England between 1997 and 2000. The aim of the study was to establish whether field margins, as set up and managed under Countryside Stewardship Scheme guidelines, were beneficial to common farmland butterflies. Thirteen two metre margins (total length 4478 m) and three sections with no margin (total length 656 m) were monitored over the 4 year period using the transect method. Significantly more Maniola jurtina, Thymelicus sylvestris and Thymelicus lineola were seen on the two metre margins than on the control sections, but there was a significant reduction in abundance of Thymelicus sylvestris, Thymelicus lineola and Ochlodes venata on the margins over the 4 year study period. Only the abundance of Pyronia tithonus increased significantly on the two metre margins over that period.

Countryside Stewardship Scheme and butterflies: a study of plant and butterfly species richness

Butterfly and plant species richness were recorded from 1997 to 2000 on 2 and 6 m grass margins created at three farms in Essex which had entered the Countryside Stewardship Scheme (CSS) in October 1996. On both the 2 and 6 m margins there was a significant relationship between the length of hedgerow and the number of plant species observed on the margins, but the seed mixtures used may not have been ideal and natural regeneration should not have been used on the clay soils of Essex. Butterfly species richness was significantly greater on the 2 m margins than on the control sections, and was greater when a higher number of grass species were included in the original seed mixture. Plant species richness was greater on the 6 m margins when established by natural regeneration. CSS grass margins could be improved as butterfly habitats if they are linked to existing habitats such as hedgerows, are sown with a better range of native grasses and herbs and are managed in a way more conducive to wildlife. These changes to the policy of establishment of CSS margins could help combat habitat loss and fragmentation within the countryside.

Pitfall trapping of scarce Orthoptera at a coastal nature reserve in Essex, UK

The value of pitfall trapping was questioned in a recent review of methods for sampling Orthoptera in grassland ecosystems. However, subsequent to the publication of this review, interesting data has become available from pitfall trapping at Colne Point, an important coastal nature reserve in Essex, UK. As a result of this trapping, the nationally scarce and Essex Red Data List species, Platycleis albopunctata, was rediscovered in the county. This tettigoniid was believed to be extinct in Essex as previous visual searches for the insect at Colne Point had failed to locate it. Large numbers of the Essex Red Data List species, Myrmeleotettix maculatus, were also captured, as were specimens of the nationally scarce cockroach, Ectobius panzeri (Dictyoptera). Systematic pitfall trapping at Colne Point was therefore pivotal in recording scarce species such as P. albopunctata which had proved difficult to locate by visual searching methods.

The effect of pasture improvement and burning on Orthoptera populations of Culm grasslands in northwest Devon, UK

Abstract Very little research has been conducted into the impact of grassland management on insect populations of Culm grasslands located in northwest Devon, UK. This paper presents the effects of agricultural improvement and burning on Orthoptera populations of these wet, heathy pastures at Dunsdon National Nature Reserve. The results from this 2-year study should aid conservation management of this important UK habitat. Orthoptera populations and habitat variables of improved (drained and cropped from 1840-1875) and unimproved pastures, were monitored in 2002 and 2003. There was no significant difference in Orthoptera abundance between pasture cropped from 1840-1875 and unimproved grassland, suggesting that mobile grasshopper species such as the meadow grasshopper Chorthippus parallelus, recolonised the improved swards from surrounding pastures, after a lengthy period of arable cropping in the 1800s. Winter burning led to higher numbers of Orthoptera in the post-burn year, perhaps due to the reduced sward height and biomass on the burnt swards, making them more favorable for postdiapause development.

Orthoptera of crossfield and headland footpaths in arable farmland

Abstract A study was made of Orthoptera assemblages of crossfield and headland (field-edge) public footpaths in the Chelmsford area of Essex, UK, in 2006. Orthoptera populations were monitored using a standardised transect counting procedure in both footpath types to determine whether headland footpaths provided benefits to Orthoptera on intensively managed farmland. Species richness of Orthoptera was significantly higher on headland footpaths (6 species) than on crossfield rights of way (3 species), suggesting that footpaths along the edges of fields may provide refuges in arable farmland. It seems that the absence of regular ploughing on the headland footpaths may be beneficial to mesophilous grasshopper species, the crossfield footpaths constituting too much of an ephemeral habitat (due to annual ploughing and cropping) to support the full range of species. Abundance of all Orthoptera and of individual species was not significantly higher on headland footpaths, although replicates on the sheltered and sunny eastern side of hedgerows had relatively high densities.

Observations of Swimming Grasshoppers in an Acid Pool in Epping Forest

Abstract Swimming behavior of the meadow grasshopper Chorthippus parallelus (Orthoptera: Acrididae) was observed in an acid pool on Sunshine Plain in Epping Forest, UK. To quantify the success or otherwise of attempts at swimming by grasshoppers, I spent 2 h watching C. parallelus nymphs on 7 June 2009. Early-instar nymphs of C. parallelus were observed to commonly use their hind legs in a kicking motion to swim in the surface film of the pool. These nymphs managed to reach the edge of the pool, whereas two late-instar nymphs (probably 3–4) after becoming submerged for more than 3 min, did not manage to exit the pool. Various escape strategies were used by late-instar nymphs that became submerged, including an underwater ‘hop’ and climbing up rush (Juncus) stems.