Methods Frequently Used in Orthopterological Field Studies

A test on the effectiveness and selectivity of three sampling methods frequently used in orthopterological field studies

Antal Nagy, Péter Sélymos & Istvan A. Racz

Nagy, A., Sélymos, P. & Racz, I. A. 2007: A test on the effectiveness and selectivity ofthree sampling methods frequently used in orthopterological field stud-

ies. — Entomol. Fennica 18: 149—159.

To obtain unbiased data in entomological samplings the selectivity and effectiveness of methods should be known. Sweepnetting, direct search and dish trap, which are frequently used in orthopterology, were tested to get data on selectivity and effectiveness. Based on the number of collected individuals, sweepnetting was the most labour efficient, while the highest number of species was collected by direct search. Dish traps were most selective to ground-dwelling species. Sweepnetting and direct search were sensitive to grass-dwelling species. Our results underlines that none of the methods is universal, and a combination of sweepnetting and direct search provides the greatest benefits.

A. Nagy, Evolutionary Genetics and Conservation Biology Research Group of the Hungarian Academy ofSciences, University ofDebrecen, P. 0. Box 3, 4010 Debrecen, Hungary; Address ofcorrespondence: University ofDebrecen, Fac— ulty ofAgricultural Science, Department ofPlant Protection, 4032 Debrecen Bo'szo'rme'nyi str. 138., Hungary; E—mail.‘ [email protected] P. Solymos, Department ofEcology, Faculty of Veterinary Science, Szent Istvan University, Rottenbiller Str. 50, 1077 Budapest, Hungary; E—mail.‘ Solymos.Pe— [email protected] I. A. Racz, Department ofEvolutionary Zoology and Human Biology, Faculty of Sciences, University ofDebrecen, P. 0. Box 3, 4010 Debrecen, Hungary, E— mail: [email protected] Received 4 July 2006, accepted 23 October 2006

1. Introduction 2001) which makes them sensitive to changes of habitat structure (Bock & Bock 1991, Chambers The study ofspecies distributions and community & Samways I998, Gebeyehu & Samways 2002). composition are essential elements in biodiversi- Based on their sensitivity, relatively high species ty assessment, monitoring and adaptive manage- richness (i. e. 120 species in Hungary, Nagy ment (Colwell & Coddington 1994). In Hungary, 2003), and easy sampling and identification, grasslands represent a major and frequent habitat orthopterans are commonly used as indicators of type, in which orthopterans constitute an impor- habitat heterogeneity, ecosystem biodiversity tant group of herbivorous insects. Herbivorous and environmental stress (Andersen et al. 2001). insects such as Orthoptera are often involved in Ideally, unbiased data on both species rich- ‘bottom—up’ resource control (Andersen et al. ness and relative abundances of species in com- 150 Nagy et al. ° ENTOMOL. FENNICA Vol. 18 munities are necessary for the inventory and later. In the second quadrat at each site, dish trap- monitoring of biological diversity. Sampling ping was running continuously for ten days. In methods for the estimation of the abundance of this manner we essentially made a repeated mea- individual populations (e. g. distance sampling sures analysis, where each sampling method was and capture-mark—recapture methods) are often used on each subject but care was taken to ensure impractical and too expensive to implement for that use of any one sampling method did not in- all species of a community. Therefore indices of fluence the results ofany other sampling method. population abundance (e.g. number of individu- Each sampling was made by A. N. The study was als caught, heard or seen) are used in most studies. conducted from 4.—14.VIII.2004. Utilization of these indices in statistical analyses Direct search (searching) is appropriate for and translation of them into estimates of species collecting presence/absence data and can be used diversity assumes that ratios of indices estimate parallel with sweepnetting (Kruess & Tschamtke relative abundances; that is individuals ofall spe- 2002, Batary et al. 2007). The samples were cies are equally detectable and all species are de- taken by walking along parallel transects in the tected (Yoccoz et al. 2001). In order to reduce sampling quadrate for 30 minutes. The width of bias in the data as much as possible, the selectiv- the transects was 1.5 m and the distance between ity, effectiveness and accuracy ofmethods in dif- transect was at least 2 m. The total length of ferent conditions should be known and sampling transects depended on vegetation structure, and strategies should be developed. density of Orthoptera-assemblages. All observed Here we compare three sampling methods specimens were recorded in units oftwo minutes, (sweepnetting, direct search and dish traps), that and each specimen was recorded only once. are widely used in orthopterological studies Sweepnetting (netting) is the most common (Balogh 1958, Ausden 1996, Murkin et al. 1996, method for collecting presence/absence and Gardiner et al. 2005). We compare the effective- abundance data on orthopterans (Southwood ness and the selectivity of these methods with re- 1978, Evans et al. 1983, Dunwiddie 1991, Cigli- spect to habitat structure. Whereas the limits of ano et al. 2000, Gardiner et al. 2005). A total of application of these methods are known (South- 300 sweeps were taken per site using a sweep-net wood 1978), we focus on fine scale differences of 40 cm in diameter. The net was emptied after among the methods, that can modify the outcome every 25 sweeps. Both search and netting were of the sampling. Based on the results we provide carried out between 9 am and 5 pm, in calm and practical recommendation on the optimal use and sunny weather. combination of these methods in orthoptero- Sampling by traps (trapping) is less widely logical research. used in orthopterological studies than sweepnetting and direct search (Gardiner et al. 2005). Pitfall traps are generally used for sampling 2. Materials and methods ground-dwelling crickets (e. g. Grylloidea, Rebek et al. 1995, Sperberg et al. 2003) and for simulta- 2.1. Study sites and sampling procedure neous sampling of different arthropod taxa (e. g. Poulin & Lefebvre 1997). Landsberg et al. (1997) The effectiveness and selectivity of three samp- and Clayton (2002) used small traps (7 and 8 cm ling methods (sweepnetting, direct search and in diameter and 12 and 11 cm deep) to quantify dish trap) with respect to vegetation structure abundance but these are preferably useful to esti- were compared. Twelve sampling sites of differ- mate incidence of species but not abundances of ent habitat structure were studied in the Aggtelek Orthoptera (Bieringer & Zulka 2003). To sample Karst region (NE Hungary), which is part of the Orthoptera (Acrididae, Tettigoniidae and Grylli- Aggtelek National Park, near Josvafo village dae) traps with larger diameter can be used e. g. (48°28’59”N, 20°33’03”E). We sampled two 25 funnel and dish traps (Duelli et al. 1999, Racz et X 25 m quadrats per site, 10—15 meters apart. In al. 2003). In this study, dish traps (a kind oflarge one of these quadrats direct search was carried pitfall trap) were used, which are appropriate for out first, followed by sweepnetting two days sampling both grass-dwelling and ground-dwell- ENTOMOL. FENNICA Vol. 18 ° A test on sampling methods OfOrthoptera 151

Table 1. Mean abundance ranks and life forms of the orthopterans collected in 12 sampling sites of the Aggtelek Karst by three sampling methods. Species are sorted according to increasing mean abundance rank. Life forms: ch: chortobiont, fi: fissurobiont, g: geobiont, th: thamnobiont, transitional life form types are in parentheses (Racz 1998).

Species Sampling type Life forms search net trap

Chorthippus parallelus (Zetterstedt, 1821) 3 1 1 ch Pholidoptera fallax (Fischer, 1853) 1 2 3 ch Euthystira brachyptera (Ocskay, 1826) 2 3 6 ch Metrioptera bicolor (Philippi, 1830) 4 5 5 ch Chorthippus apricarius (Linnaeus, 1758) 7 8 4 ch Stenobothrus crassipes (Charpentier, 1825) 5 6 9 ch Omocestus haemorrhoidalis (Charpentier, 1825) 10 4 7 g (ch—g) Calliptamus italicus (Linnaeus, 1758) 6 7 8 g (g—ch) Leptophyes albovittata (Kollar, 1833) 8 9 16 th Glyllus campestris Linnaeus, 1758 14 18.5 2 fi Stenobothruslineatus (Panzer, 1796) 12 13 11 ch Phaneroptera falcata (Poda, 1761) 9 11 23 th Decticus verrucivorus (Linnaeus, 1758) 11 22.5 10 th (ch—th) Stauroderus scalaris (Fischer de Waldheim, 1846) 16.5 18.5 12 ch * Poecilimon fussi Brunner von Wattenwyl, 1878 21.5 12 — th Chorthippus dorsatus (Zetterstedt, 1821) 18.5 18.5 13.5 ch Chorthippus brunneus (Thunberg, 1815) 18.5 14.5 18 ch Pachytrachys gracilis 20 18.5 13.5 th (Brunner von Wattenwyl,1861) Psophos stridulus (Linnaeus, 1758) 13 24 15 g (g—ch) ** Chorthippus mollis (Charpentier, 1825) —— 18 g (ch—g) Tetrix bipunctata (Linnaeus, 1758) 24 10 20.5 ch Metrioptera brachyptera (Linnaeus, 1761 ) 16.5 22.5 20.5 ch Pseudopodisma nagyi Galvani et fontana, 1996 15 18.5 28 ch Gomphocerippus rufus (Linnaeus, 1758) 23 14.5 28 ch Platycleis albopunctata (Goeze, 1778)* 26.5 — 18 g (ch—th) lsophya kraussii Brunner von Wattenwyl, 1878 21.5 18.5 28 ch Omocestus rufipes (Zetterstedt, 1821)* — 25.5 23 ch Pholidoptera griseoaptera (DeGeer, 1763) 25 25.5 23 th * Arcyptera fusca (Pallas, 1773) 26.5 28 — g (ch—g) Paracaloptenus caloptenoides — 28 — g (Brunner von Wattenwyl,1861)** Chrysocraon dispar (Germar, [1834]) 28 28 28 ch Chorthippus biguttulus (Linnaeus, 1758) 33 28 28 ch Saga pedo (Pallas, 1771)* 33 28 — th (ch—th) ** Tettigonia viridissima Linnaeus, 1758 33 —— th Ruspolia nitidula (Scopoli, 1786)** 33 —— th ** Mecostethus parapleurus (Hagenbach, 1822) 33 —— ch Omocestus petraeus (Brisout de Barneville, 1856)** 33 —— g (ch—g) ** Oedipoda coerulescens (Linnaeus, 1758) 33 —— g Oecanthus pellucens (Scopoli, 1763)** 33 —— th (ch—th) Chorthippus oschei Helversen 1986** 33 —— ch

* species that are missing from only one method out of the three ** species that are unique to only one method ing Orthoptera. We used brown coloured flower- (25 v/v%), detergent, formaldehyde (5 v/v%) and pots (20 cm in diameter and 20 cm deep) as traps. water was used as killing liquid and preservative. The traps were dug into the soil, and the vegeta- The ethylene-glycol slowly evaporates and the tion was left intact. A mixture of ethylene-glycol detergent decreases the probability of specimens 152 Nag}; 6t dz“ 6 ENTOMOL. = 1(:A(VJCflJ:l8

Table 2. Vegetation structure, number of Orthoptera species (8.0.3,) and individuals (News!) in the studied sites (1—m- 12).

Sites Cover Height (cm) (%) State, iota,

flower upper lower upper

1 32.8i4.2 75.8:175 95 1 16 234- 2 334$] 82.41112 85 12 20 34-2 3 34.5s44 84.51104 85 10 20 381 4 34.4%.”! 79.9s9.3 95 15 17 521 5 30.1i5.2 72.2i94 95 40 M- 357 6 18.6s3.8 68.9fl42 60 2 20 262 7 26.1s4.9 59.5fl 0.9 55 5 ’19 229 8 19.2s2.9 63.0s155 80 1 18 258 9 29.5i3.9 65.1i13.5 60 5 13 2‘17 10 30.7i3.3 65.5i115 60 5 20 255 11 23.7i5.3 51.8fl3] 95 15 ’18 638 12 258:4.6 70.9i8.1 7O 12 19 257

escaping from the traps. Traps were exposed. for the two grass layers estimated in field (Table 2). ten days and were emptied every two days. Parameters of the vegetation structure were sub-- For identification of the collected specimens. jected to principal component analysis (PCA). keys of Harz (1957. 1.969. 1.975) were used. For Along the first principal axis. two groups of sites nomenclature. we followed jeHer er a2. (1998). were separated. The first group is characterised by short grasses (sites 6—12. short type). While the second by dense and tall grasses (sites 1—5. taH 2.2. lam alysis type). used these two grass types in further analyses (Table 2. Fig. 1). Species were grouped into life types. based We were concerned about the abundance on the classification by Récz (1998). Based upon their body shape. habitat preference and. physio- 3 .. logy. orthopterans can be classified into four pri- mary life f0 types (Récz 2001). obioms ‘11 5 "" live in the canopy and dense grass. choflobioms 2 O sessss are grassmdwefling. geobients prefer sparse and and fissumbionts dwell on the open grasslands. 1 ..

are (I) to their there "'"' ground. According behaviour. 8 transitional Le. «E 0 rther. types. ch.0rt0~thamn0~. "U 12

'"" O and (g 0 g 7 0~ch0rt0~. ch0rt0~geo~ geowchortO-u 00 9 biont (Récz 1998. 2001). in this study only pri- 5325 01C? :sssss 3 were mary types used because of insufficient “1“ :u number of cases oftransitional types. in this case the obioms also include thaomchorton and

"'2 i s i i Chortomthaobionts. while geobionts also in»: -2 1 O 1 2 elude geomchortom. and Chortomgeobionts (Table istAxh l). Fig. 1. Groups of sites according to principal compo-:- was characterised mean Vegetation by nent anaiysis based on four variables of vegetation ofthe lower and. calm-«- heights upper grass layer. structure (see Table 2). Empty dots: short grasses, lated from measurements made in ten random filled dots: tail grasses. Labels of the dots refer to the points 0fthe 25 X 25 m quadrates and. by cover of numbers of sites in Table 2. ENTOMOL. FENNICA Vol. 18 ° A test on sampling methods OfOrthoptera 153 ranks of the species and not about their absolute (Mauchy’s test of sphericity, p>0.2). abundance or relative frequency values. Thus we To analyse the selectivity of the methods, we used Kendall’s concordance based on ranks (Zar determined the number ofunique species for each 1984) to test within-group agreement of abun- method (SW) and the proportion of life forms in dance ranks of the species in samples collected the samples. Because these variables were not with the same method for each grass type. The be- distributed normally even after a logarithmic tween-groups agreement of the species’ abun- transformation (Shapiro-Wilk test, p<0.05), we dance ranks was tested by two group concor- used nonparametric two-way analysis ofvariance dance (Schucany & Frawley 1973). (Zar 1984) with number of unique species for To analyse the effectiveness of the three each method and the proportion of life forms as methods, we compared species accumulation dependents, and method and grass type as factors. curves specific to each method. For the estima- We excluded two short type sites (11 and 12) tion ofthe parameters ofthe species accumulation characterised by intermediate PCA scores (Table curves we used the Clench equation (Soberon & 2, Fig. 1) to get equal number of replicates (n=5) Llorente 1993): within each treatment combination. Because samples taken by the three methods in the same S(n)=an/(1+bn) site are not independent, they can be considered as repeated measures. Therefore, we performed where S is the number of species, n is the number Friedman’s nonparametric analysis of variance of sampling units, and a and b are constants esti- with method as repeated measures separately for mated from the data. As Willott (2001) suggests, the two grass types when the method >< grass type we used the number of individuals in the subse- interaction was not significant. We used the quent samples — not sampling units (i.e. time in- Wilcoxon signed rank test for pairwise compari- tervals and net samples) alone — as the measure of sons of related samples. sampling effort to use uniformly scaled inde- We further tested the association between pendent variable in the extrapolation of the spe- method-specific presence (”unique species” cies accumulation curves. The sample orders sampled by only one of the three methods in a were not randomized because sampling units given site) and absence (species not sampled by were taken continuously in time. only one of the three methods in a given site) of For each method in each sampling site, we de- species and life form categories by multinomial termined the observed number of species (Sam), logistic regression. Method-specific presences the estimated maximum number of species and absences of species were treated as multi- (Smafa/b; Soberon & Llorente 1993), the ex- nomial dependent variables (categories indicated pected number of species associated to the mini- the method by which the species was caught or mum number of individuals observed in samples not caught) and were analysed separately. Trap- (33 individuals) (5M3), and the estimated number ping was treated as the reference category. Life of individuals necessary to detect the minimum form categories ofthe species caught were factors number of species observed in all samples (5 spe- in the model. Species identity as independent cies) (NS5). These dependent variables were log- variable was not evaluated due to inadequate transformed. We used the values of species rich- sample size and unbalanced species distribution ness, effectiveness and selectivity (described among the levels of factors. above) of the 12 sites as subjects, and compared by general linear models (GLM) with repeated measures. Methods were treated as repeated mea- 3. Results sures and grass type as fixed factor. Significance levels for multiple comparisons were adjusted by A total of 40 Orthoptera species (16 Ensifera: 14 the Bonferroni method (Motulsky 1995). The er- Tettigonioidea, 2 Grylloidea and 24 Caelifera) ror covariance matrices of the orthonormalized were found (Table 1). When all data were sum- transformed dependent variables were propor- marised according to methods, the five highest tional to the identity matrices respectively ranking species were Chorthippus parallelus,

ENTOOL, FE lCA Vol. 18 a A test on sampimg methods OfOFZ‘hopl‘era 155

Table 4. Results of the Wile-way nonparametric analysis of variance analysing the effect of method and grass type on the number of unique species (SW) and the proportion of life forms (Th: thamnobionts, Ch: chonhobionts, Geo: geobionts, Fi: fissurobionts) on 10 sites (equal number of replicates, ie. 5 + 5, were needed within each treatment combination; Zar 1984)..

Sm Proportion of life forms

Th Ch Geo Fi

Total 77.5 77.5 77.5 77.5 77.5 (dsz) 88 817.4 45.1 84.2 60.2 1376.6 H 10.55“ 0.58ns 1.09% 0.78% 17.76""M Grass (dfx’i) 88 132.3 19.2 340.0 381.6 64.5 H 1.71% 0.25% 4.39"“ 4.92"k 0.83ns interaction (df-zZ) 88 46.6 18.1 101.7 77.3 15.3 H 0.60% 0.23ns 1.31m 1.00ns 0.20m

SS: sum of squares of ranks. MS: mean square ns: not significant, *: p<0.05, **: p<0.01, ***: p<0.001. thcds (Table 3). Effectiveness increased from fects cfgrass type and interaction were not signif— trapping through search to netting and netting icant (Table 4). The effect of method in tail perfo marginally better than trapping grasses was significant (Friedman test. x2=6.0, Bonferroni Grass n35 and the number of (p<0.1, correction; Fig. 2). type off-+2. 9 p<0.05) unique spe- and the interaction. of the llWO factors had no Sig- cies increased. from netting through trapping to nificam effect on the independent variables in. sin searching. Searching perfo-ed marginally ther comparison (Table 3). better than netting (p<0.l, onfermni correcw The number of unique species (SW) differed lion). in short grasses? the difference among significantly among the methods, Whereas the cf"- methods was marginally significant (Friedman test. x2=4.73, off—4:25 n37. p<0.l). and pairwise revealed a to that in tall 'iiijijiiizéaa 90 -- comparisons tendency d grasses (Fig. 3). 80 "— 3 The sampling methods were roughly equally effective in detecting Obiont, chonobion‘t and The was the m 60 ... geobiont species. only exception a? detection of fissumbioms because the proportion .. c 50 -- d) a) x a. of fissumbiont life differed significantly U ...... “ g 40 ~— S among the methods (Table 4). Trapping wiper-- “\ s é fc the other two methods in. both short E3 30 - :5 \ z \ 5f \ 1 .. \- (Friedman test. X22120, dfiZ. n37. p<0.0l; for 20 ~— \ b \ post-hoe tests: p<0.05., onfermni correction) 1 o and tall grasses (Friedman test? 9639.294, off—1:2. for tests: B

._ ...... 1”...... I...... §5§5§5§5§5§5§5§5§5§5 .. .. 0 \ ._.. Iiiiiiiiiiiiiiiiiiiiiii \\ n25. p<0.0l; postuhoc p<0.l. O I Th 8 fermni The of oh diff correction) (Fig. 3). proportion the Obiont. Chofiobiom: and geobiom: life f0 i Fig. 3. SE of the studied variables quantifying >< did not differ among methods and the grass selectivity of the three studied methods. ._.._ a. Proper- method interaction was also not significant al— tion of thamnobiont (Th), Chortobiont (Ch), geobiont the of Chofiobiom: and (Geo) and fissumbiont (F1) life form. —--- b. of though proportion life differed bem- unique species (Sm. ). Variables are grouped according geobiont significantly to measurement scale. Different letters indicate signifi- tween short and tail grasses (Table 4). Chofiom cant (p<0.05) differences according to paiswise com- bionts were more abundant (mean proportion in pansons. short grasses 70.6 i 13.3 SD. in tall grasses 83.5 i 156 Nagy et al. ° ENTOMOL. FENNICA Vol. 18

Table 5. Association between life forms and the selectivity of the methods studied by multinomial logistic regression. Table includes counts of individual catches and beta coefficients for presences and absences that were specific to each methoda.

Life formb Chortobiont Fissurobiont Geobiont Thamnobiont

Count Beta Count Beta Count Beta Count Beta

Presence Searching 13 0.26ns — —20.15na 7 1.95+ 11 0.61ns Netting 4 —0.92ns — —20.15na 1 0.00ns 2 —1.10ns Trapping 10 ref. 5 ref. 1 ref. 6 ref.

Absence Searching 7 —1.15** 1 19.08*** — —19.82na 2 —2.20** Netting 10 —0.79* 4 20.47na 3 —0.29ns 6 —1.10* Trapping 22 ref. — ref. 4 ref. 18 ref. a Method specific presences and absences of species were treated as multinomial dependent variables and were analysed sep arately (trapping was treated as reference category). b Life form categories of the species caught were included as factors in the model. ref.: reference category. na: significance not assessed due to the lack of variance or low sample size, ns: not significant, +: p<0.1, *: p<0.05, **: p<0.01, ***: p<0.001.

10.9 SD), while geobionts were less abundant in the need for development of standardised samp- tall grasses (mean proportion in short grasses 14.8 ling methods and strategies that can provide com- i 10.0 SD, in tall grasses 4.1 i 3.1 SD). parable data on abundances and species richness. Analysis of between method-specific pres- In the present study we compared three of the ences and life forms revealed that searching was most frequently used methods in Orthoptera as- selective for geobionts (96:30.52, dF8, sessments. We focused on the effectiveness and p<0.001). The association was also significant selectivity of these methods with regard to fine (96:37.07, dFS, p<0.001) for method-specific scale effect ofhabitat structure. Our study also in- absences. Fissurobionts were highly likely to be cluded two groups of Orthoptera that have not missed by search method and netting. Species, been extensively studied, namely bush-crickets that were absent by either netting or searching, (Tettigonioidea) and crickets (Grylloidea). were likely not chortobionts or thamnobionts Among the three studied methods, search pro- (Table 5). vides the most complete list of observed Orthoptera species, because it is more sensitive to rare species than netting and trapping. However, 4. Discussion considering sampling effort in terms of the number ofindividuals sampled, netting is the most ef- A great deal of work has been published on im- fective. Although trapping is not a common provement (eg. Falkenbury & Vemer 1970, method for sampling orthopterans and it is less ef- Wrubeski & Rosenberg 1984, Sperberg et al. fective than the other two methods, it can be use- 2003) and comparison (eg. Morgan et al. 1963, ful when more, mainly ground-dwelling inverte- Evans et al. 1983, Sparrow et al. 1994) of samp- brate taxa (e.g. Myriapoda, Opiliones, Ortho- ling methods used to estimate species richness, ptera, Coleoptera: Carabidae, Silphidae, Geotru— abundances and population size ofinsects. Gardi- pidae, Scarabaeidae etc.) are sampled simulta- ner et al. (2005) reviewed the methods for popu- neously. Another advantage of trapping is that lation estimates of Orthoptera, particularly grass- this method is easier to standardise (Murkin et al. hoppers (Orthoptera: Acrididae). The authors 1996), an important requirement to get unbiased critically reviewed 112 publications and pro- data (Duelli et al. 1999). Since in case oftrapping vided useful suggestions for researchers on the the distribution of thamno-, chorto-, and geo- use of eight sampling methods. They highlighted bionts were similar and abundance ranks were ENTOMOL. FENNICA Vol. 18 ° A test on sampling methods OfOrthoptera 157 positively correlated according to the between field, while all individuals collected by volun- group concordance values, larger traps, as used in teers need to be stored or killed and subsequently this study, can be useful in quantitative data col- identified in the laboratory, which increases the lection. The diameter ofthe trap may have signif1— disturbance associated with sampling. cant effect on effectiveness and selectivity as Sampling methods also differ in their applica- well. bility in different habitats. Although in this study To detect a minimum number of species (five the effect ofvegetation structure could not be de- species in this study), it is necessary to collect tected, standard sweep net is not applicable in ex- more individuals when using traps than with the tremely dense or sparse vegetation (Southwood other methods in short grasses. In tall grasses, 1978).The applicability of trapping strongly de- sampling effort (number of individuals sampled pends on quality and depth of soil and bedrock, to get the same species richness) increases from because relatively large traps can not be dug into netting through searching to trapping, out of rocky surface or shallow soil. Search can be used which trapping is the most labour-intensive and in a wide range of habitats but it is difficult to time-consuming, especially in the field. standardise because it is highly subjective. This In this study, searching was selective to rare effect decreases in the search-netting-trapping di- species and the number of unique species was rection. highest in this method. Consequently, trapping Our results suggest that none of the methods overestimated the proportion of fissurobiont life can be used universally thus one has to choose form in the assemblages. Based on specific ab- among methods based on the goals of the given sences, direct search and netting were less sensi- study, its data requirements and the advantages tive to fissurobionts, while both search and net- and disadvantages of possible methods. In order ting were more sensitive to chorthobionts and to collect rare species and make complete check- thamnobionts than dish trapping. The similar se- lists searching is the most appropriate. Ifwe need lectivity ofsweep netting and direct search makes a well standardised and effective method to col- the comparison between samples and combina- lect quantitative data we should use sweep- tion of these two methods more feasible. When netting. When the aim is to gain data on more trapping is combined with other methods, meth- ground-dwelling taxa simultaneously dish-trap- ods may complement each other’s selectivity. ping has the most advantages. Considering the Sampling effort consists of two important different selectivity and restrictive applicability components: manual-labour (e. g. collection ofin- of methods, overall sampling bias can be de- dividuals, setting, checking and emptying traps) creased by combining them, because methods and intellectual achievement (identification of can complement each other. Since the abundance specimens). Although manual-labour can be car- ranks showed significant positive correlations, ried out by both specialists and volunteers, the in- the combination of methods can be used in both tellectual achievements needs specialists’ knowl- quantitative and qualitative studies. Combination edge. In case of netting and trapping these two ofnetting and direct search appears to provide the parts can be carried out by different persons, most advantages. Such a combination can be used however, direct search can only be done by spe- in a wider range of habitats, it requires less man- cialists. The participation ofvolunteers or profes- ual labor and identification skills and volunteers sional staff assisting in monitoring and inventory can participate in field work. This combination programs increases public awareness and recep- provides the most complete list ofspecies, it is the tion of the research project and reduces the costs most cost effective and causes less disturbance to of manual-labour, although it comes with some habitats and insect communities than other com- shortcomings. On the one hand, volunteers can- binations of methods. not conduct efficient direct search, which is most Acknowledgements. The authors thank the staff of the sensitive to rare species, thus they usually have to Aggtelek National Park for permissions, Sz. Lengyel, P. collect more individuals than specialists to detect Batary, Z. Barta and two anonymous reviewers for critical the same richness. On the other species hand, spe- comments on an earlier version of the manuscript. cialists can identify most of the individuals in K. Szlavecz improved the English. 158 Nagy et al. ° ENTOMOL. FENNICA Vol. 18

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