1998. P. A. Selden (ed.). Proceedings of the 17th European Colloquium of Arachnology, Edinburgh 1997.

Seasonal activity of the ground fauna in a Mediterranean ecosystem (Mt Youchtas, Crete, Greece)

M. Chatzaki1,2, A. Trichas1, G. Markakis2 and M. Mylonas1

1Natural History Museum of the University of Crete, Knossou Av., 71409 Irakleio, Crete, Greece 2Dept of Biology, University of Crete, 71100 Irakleio, Crete, Greece

Summary Arachnological data on the ground faunas of the eastern Mediterranean island ecosystems are very scarce, usually concerned with descriptions of new taxa or reviews of distributional data of the known species of the area. An ecological approach is limited and almost absent at post-family level. The scope of the present work is the structure of the spider community (family and species compo- sition) as well as spider kinetic activity during the period of one year, in a Mediterranean phryganic ecosystem (north-east slopes of Mt Youchtas, 16 km south of the city of Irakleion, Crete). were sampled monthly, using 25 pitfall traps placed under the dominant plant species of the site (Broom, Thyme and Kermes Oak) and on the open ground. A total of 1845 individuals were cap- tured throughout the year, belonging to 21 families and 61 species. The dominant families as far as both species richness and abundance are concerned were Gnaphosidae, and Salticidae, with the rest of the families much less well represented. Seasonal variation revealed three basic pat- terns of activity, indicating differences in life style and responses to environmental factors. Spatial variation was limited only by minor differences between open ground areas and those covered by the dominant plants of the site.

Introduction Arachnological data on the ground faunas of ecosystems in Greece have been provided by Spiders are generalist feeders with great researchers such as Brullé (1832), Lucas (1853), species richness in every type of terrestrial habi- Kulczyn´ski (1903), Strand (1916), Roewer tat, and therefore they play an important role in (1928, 1959) and Bristowe (1934), who the structure of communities and food webs, presented lists of the spider species of several both as number of individuals and as energy continental and insular sites of Greece with consumers (Post & Riechert, 1977; Foelix, some ecological notes. A more detailed study of 1982; Fasola & Mogavero, 1995). These fea- the region was carried out later by Brignoli, who tures make them ideal models as terrestrial produced many papers on spider with predators in community analyses (Post & biogeographical notes, in the period 1968–1986 Riechert, 1977; Wise, 1993). Ecological studies (Brignoli, 1984, and references therein, 1985, of this kind have been presented in the past, 1986). He concentrated mainly on cave spiders. mainly concerning the relationships between Contemporary researchers are making further taxonomically well-defined groups of spider contributions with descriptions of new species species in regions in which problems on spider and/or distributional data on the spider fauna of taxonomy are more or less resolved. Knowledge the same area. of species composition and distribution in east- Species catalogues on a national or regional ern Mediterranean ecosystems is very limited, level are still unavailable for Greece, while the making ecological studies in this region very contribution of Greek scientists has been limited difficult. (Chatzisarantos, 1940; Paraschi, 1988). 236 Proceedings of the 17th European Colloquium of Arachnology, Edinburgh 1997

THE THO including dwarf, aromatic and thorny shrub CL 3% 2% 2% species characteristic of the Cretan landscape OT 10% such as: Genista acanthoclada, Coridothymus CT 4% capitatus, Ebenus creticus, Salvia fruticosa, ZO 4% Asphodelus aestivus, Cistus creticus, as well as taller shrubs of Quercus coccifera. Plants cover DY 6% about 80% of the site; the remaining 20% is open ground. The area chosen for this study, although quite close to urban, pastural and agri- LI 11% cultural regions, is undisturbed by human activ- ities (grazing of is prohibited), and has been proposed for inclusion in the NATURA 2000 EEC network of protected areas (on account of high levels of biodiversity and plant SA 13% endemism). It is quite close to the University, facilitating monthly visits. GN 45% Twenty-five pitfall traps were placed under the dominant plant species (Quercus coccifera, Genista acanthoclada, Coridothymus capitatus, Fig. 1: Dominant spider families on an annual scale. Ebenus creticus, Salvia fruticosa) and on the GN = Gnaphosidae, SA = Salticidae, LI = open ground. The traps were plastic cans (12 cm Linyphiidae, DY = Dysderidae, ZO = Zodariidae, high, 9.5 cm diameter); the killing agent and CT = Ctenizidae, CL = Clubionidae, THE = Theridiidae, THO = Thomisidae, OT = Others. preservative fluid used was ethylene glycol. Spiders and other were sampled monthly and the samples were sorted and stored Neither the main characteristics nor the indi- in 70% alcohol. The sampling period lasted vidual details of the Greek arachnofauna are from December 1995 to January 1997. The well known. Apart from the ecological data on results of the first twelve months are presented Greek spiders of the maquis of the central here, while data of the remaining two months Aegean provided by Paraschi (1988), no other have been used as a control. data are available on the arachnofaunas of the Spiders were sorted, identified, counted and southern Greek ecosystems. deposited in the Natural History Museum of the The present work focuses on the basic struc- University of Crete. Some of the identifications as well as species confirmations were carried ture of spider communities (family and species out by Dr K. Thaler, Institut für Zoologie, composition, dominant taxa), on the family and Innsbruck. Immature specimens were identified dominant species phenologies, as well as on the to below family level when possible. life strategies of the arachnofauna, in the south In order to equalize the number of individuals Aegean phryganic ecosystems. An effort has for each month, all monthly catches were trans- also been made to reveal spatial differentiation formed into number of individuals per 30 trap in different microbiotopes of the study area. days. Principal Component Analysis (PCA) and Materials and methods Correspondence Analysis (CA) were used for the spatial differentiation analysis for each The study area is situated on the north-eastern month (Pielou, 1984). slopes of Mt Youchtas (highest point 811 m), 16 km south of the city of Irakleion, north- central Crete, and is about 350 m above sea Results level. The substrate is calcareous with many Faunal composition and abundances stones and rocks, while the slope of the site varies between 20–40%. The vegetation can be A total of 1845 individuals were captured described as degraded maquis and phrygana, during the one-year sampling, belonging to 21 Chatzaki et al.: Seasonal activity of Mediterranean ground spiders 237 families and 61 species. Gnaphosidae can be Maimuna cf. cretica, Tegenaria sp.; classified as the dominant family (over 40% Amaurobiidae Amaurobius cf. erberi; Anyphaenidae annual representation), while the rest of the Anyphaena sabina; Clubionidae Clubiona vegeta?, families belong to influent (16–23%) or acces- Mesiotelus cf. tenuissimus; Ctenizidae Cyrtocarenum sories (below 8%), following the classification cunicularium; Dysderidae Dysdera gigas, Harpactea coccifera, H. cressa, n. sp.; Filistatidae Filistata of ´Luczak (1963) (Fig. 1). (Pritha) sp., Filistata insidiatrix; Gnaphosidae Family composition of the spider community Aphantaulax seminigra, Drassodes lapidosus, shows considerable variability from month to D. lutescens, Haplodrassus dalmatensis? H. signifer, month. Gnaphosidae represent the dominant Nomisia cf. ripariensis, Pterotricha lentiginosa, Zelotes family for most of the months, ranging from 2% (Drassyllus) sp., Zelotes cf. creticus, Zelotes sp.; (December) to 77% (May). Linyphiidae domi- Linyphiidae Gonatium sp., Lepthyphantes aff. collinus, nate during the winter and spring months, Mecopisthes sp., n. sp., Pelecopsis sp., Savignya? sp., ranging from 2% (May) to 63% (December), but Sintula retroversus, Theonina sp., Walckenaeria clavilobus, are absent during the summer and autumn. W. cretaensis; Loxoscelidae? (immature specimen); Salticidae reach their maximum abundance in Lycosidae Lycosa narbonensis; Oecobiidae Oecobius sp.; Oonopidae Oonops sp.; Oxyopidae Oxyopes September (34%). The rest of the families repre- heterophthalmus; Palpimanidae Palpimanus sp.; sent less than 10% of the total arachnofauna, Pholcidae? (immature specimen); Salticidae Aelurillus with their maximum monthly abundance being sp., cf. Aelurillus, Ballus sp., Cyrba algerina, Euophrys sp., less than 25%. Heliophanus sp., Pellenes?, Philaeus chrysops, Saitis The three dominant families, Gnaphosidae, graeca?; Scytodidae Scytodes thoracica; Theridiidae Linyphiidae and Salticidae, are also the most Crustulina scabripes, Enoplognatha thoracica, Episinus numerous as far as species richness is con- sp., Euryopis sexalbomaculata, Theridion cf. melanurum; cerned: Linyphiidae are represented by 10 Thomisidae Ozyptila confluens, Proxysticus sp., Thanatus species, Gnaphosidae by 10 species, Salticidae vulgaris, Xysticus turcicus; Zodariidae Zodarion sp. 1, by 9 species. Some families are represented by 4 Zodarion sp. 2. or 5 species (such as Dysderidae, Theridiidae and Thomisidae), while the majority of the fam- Table 1: List of species in the study area. ilies are represented by only one or two species. The commonest taxa collected at the site were Pterotricha lentiginosa (Koch, 1839), influenced by the activity of males. When Walckenaeria cretaensis (Wunderlich, 1994), mature, males become very active in the effort to Drassodes, Zelotes, Lepthyphantes, Dysdera, find a mate. Therefore, the great number in pit- Harpactea, Cyrtocarenum and Crustulina fall catches is indicative of the time of reproduc- (Table 1). tion (Tretzel, 1954; Duffey, 1962; Milner, 1988). It is interesting to note that, although the high- The spring peak is produced both by male and est numbers of spiders were collected in spring female individuals, though the autumn peak is and autumn, the greatest numbers of species formed mainly by the male activity. Immatures were reported in summer. During July there is a are more abundant during spring and late sum- maximum of families (17) represented in the mer, indicating that the reproductive period of site, while the minimum is in December (7). most of the spiders is in the spring. This coincides with observations of other When referring to the seasonal activity on a researchers on grasslands (Duffey, 1962), but in family level, three basic patterns are apparent, other cases this summer maximum in species formed by the three dominant families, richness is mirrored by similar peaks in absolute Gnaphosidae, Linyphiidae and Salticidae numbers (Merrett & Snazell, 1983). (Fig. 3). These patterns of activity fit to Phenology—temporal variation Eurychronus, Winter-mature and Stenochronous modes, respectively, as defined by Aitchison The annual spider activity in the study area is (1984). illustrated in Figure 2. Two peaks of activity Eurychronous families. Gnaphosidae are occur, one in spring (from April to June) and one present during the whole year, with two peaks of (slightly higher) in autumn (September). activity in May (males and females) and Monthly fluctuations in activity are mainly September (almost only males), while during the 238 Proceedings of the 17th European Colloquium of Arachnology, Edinburgh 1997

2 5 0

2 0 0 immatures males

females

1 5 0

1 0 0

otal catches/30 days catches/30 otal

T

5 0

0 jan feb mar apr may jun jul aug sep oct nov dec

Fig. 2: Spider phenology on Mt Youchtas. winter they are almost exclusively represented formed by the presence of male individuals only by immature individuals and some females of of Dysdera gigas Roewer, 1928. The same pat- the Zelotes. Pterotricha lentiginosa and tern is shown by Clubionidae, where the Zelotes spp. are the most abundant species, November peak is produced mainly by the males forming the main pattern of activity of the fam- of the Mesiotelus spp. ily, while Nomisia and Drassodes spp. are less Amaurobiidae seem to follow the same pattern, well represented in this pattern, being active but no safe conclusion can be drawn because of mostly during April and May (therefore showing the low numbers of specimens collected. a more stenochronus mode of activity, see Stenochronous families. Salticidae seem to Fig. 4). Members of the families Zodariidae, have a reverse pattern of activity, showing a Palpimanidae and Thomisidae can also be maximum peak in September (formed mostly by included in this category. males) and a lower one in June (males and Winter-active families. Linyphiidae constitute females), representing a more xerophilous the majority of the arachnofauna in winter behaviour. Salticidae (greatly diversified in (occupying 63% of the total catch in December), Crete) is represented by a good number of while they decline during the dry season species in the study area; when present, they are (from May to October). Walckenaeria and active almost all the time, Lepthyphantes spp. seem to have a longer period Ctenizidae, Theridiidae, Filistatidae, of activity than other species. In higher latitudes, Oecobiidae, Loxoscelidae, Pholcidae, some Linyphiidae present another peak in Scytodidae and Lycosidae follow the stenochro- autumn (Huhta, 1971); this does not occur in the nous pattern of Salticidae, being active for only study area because the temperatures in Crete are one period of the year, with the immature phase still quite high during the same period, which preceding or following. A continuous series of does not encourage a second generation of activity peaks from late summer to early autumn linyphiids. precludes any strict categorization of the above Clubionidae and Dysderidae are apparently families into seasonal types. Ctenizidae and winter-active spiders, showing a pattern of Lycosidae were mostly represented by males, activity very similar to that of Linyphiidae. All which is to be expected considering the mode of three together constitute almost the total spider life of these families—females of Cyrtocarenum catch in winter and early spring. cunicularium Olivier, 1811 and Lycosa The main peak of activity in Dysderidae is narbonensis (Latreille, 1806) do not leave their produced by all dysderid species found at the burrows for most of their lives. Most of the site. However, the second peak in November is Scytodidae collected in the traps were Chatzaki et al.: Seasonal activity of Mediterranean ground spiders 239

1 0 0 %

8 0 %

6 0 %

4 0 % SALTICIDAE LINYPHIIDAE GNAPHOSIDAE 2 0 %

0% Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Fig. 3: Relative representation of numbers of individuals of the families Salticidae, Linyphiidae and Gnaphosidae. immatures, suggesting a non-errant mode of life Analysis (PCA) was used to detect significant of adults. Oecobiidae are active almost exclu- differences among the 25 traps, depending on sively in June, with a high representation of both the composition of the families found in them. males and females. Numbers of individuals in each trap were square Theridiidae spend their lives almost exclu- root-transformed and the analysis was per- sively on the lower vegetation, so their densities formed for each month separately. When the may be much higher than those indicated by pit- first PCs were plotted there was no evident fall trapping. Little can be said about grouping of the traps relating to microbiotopes Filistatidae, Loxoscelidae and Pholcidae, due to the low number of specimens collected. and the composition of families found in them. In an overall view, stenochronous and The 25 traps were then divided into the corre- eurychronous families constitute the spider sponding microbiotopes and manipulated as six community of the dry season, which in Crete different substations to be analysed with lasts from May until October. If any specific Correspondence Analysis (CA). The analysis strategies are included in these patterns of activ- could not provide clues about any preference of ity, they seem to adapt their agents in the best a particular family to a specific microbiotope way for their survival in the dry habitats of the when viewed on an annual scale, except that eastern Mediterranean. Quercus, Thymus, and open ground produced the highest numbers of spiders. On the other Spatial variation hand, the following results can be extracted As mentioned before, the 25 pitfall traps were from the monthly analyses: placed under the dominant plant species and on • Collections from the six substations were the open ground, in order to reveal differences in quite distinct each month. the spatial distribution of spiders in the micro- • Linyphiidae showed some preference for the biotopes of the site. Principal Component Ebenus microbiotope (December to March), 240 Proceedings of the 17th European Colloquium of Arachnology, Edinburgh 1997

180

160

140

120

100

80

60

40

20

0 days Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Drassodes sp. Nomisia sp. Pterotricha lentiginosa

Zelotes sp . others total Gnaphosidae Individuals/30 Individuals/30

Fig.4: Phenology of the dominant Gnaphosidae on Mt Youchtas. though in November they seemed to prefer the Discussion open ground. • Gnaphosidae and Salticidae did not show a Although pitfall trapping selectively collects special preference for any microbiotope, being only the ground active spiders (Duffey, 1962; Southwood, 1966; Turnbull, 1973), it is, never- abundant everywhere and moving constantly. theless, a suitable method for semi-quantitative • Ctenizidae showed a drift from the open analyses—the measurement of “active density” ground (June and July) to microbiotopes cov- (Uetz & Unziker, 1976), or “penetration” ered by vegetation (August to December). (Heydemann, 1961)—and can give a compara- • Theridiidae and Thomisidae showed a clear tive measure of communities without the bias of avoidance of the open ground. The former were the different collecting abilities of researchers. found more often in the Quercus and Genista The total number of catches (1845 individuals microbiotopes, while the latter did not show any with mean density of 30.7 individuals per station evident preference. per month), as well as the number of families • Dysderidae showed a preference for the (21) and species (59) found in the study area, are Quercus microbiotope, while during July and similar to those reported by other authors in August (when only immature individuals occur Mediterranean ecosystems: 26 families in a in the site) they were also present on the open phryganic ecosystem in Lebanon (Assi, 1983); 15–17 families in arid grasslands and Juniperus ground. associations in New Mexico (Muma, 1980); 22 • Filistatidae tended to be present more fre- families in a Quercus coccifera association in quently on the open ground through the whole southern France (Bigot & Bodot, 1972); and year. 20–22 families in the maquis ecosystem of • Agelenidae showed some preference for Epidaurus and Naxos in Greece (Paraschi, Genista and Salvia. 1988). These numbers, when compared with • Oecobiidae occurred more frequently on the similar studies from other types of ecosystems in open ground. central Europe, suggest that the heterogeneity of Chatzaki et al.: Seasonal activity of Mediterranean ground spiders 241

Mediterranean ecosystems, especially the The spider phenology of the study area coin- insular ones, produces higher diversities, but cides with these of other arthropods in lower population densities (Di Castri & Vitali- Mediterranean ecosystems (Di Castri & Vitali- Di Castri, 1981). Di Castri, 1981; Lamotte & Blandin, 1989; In overall view, wandering, ground-living Magioris, 1991), presenting two peaks of spiders dominate the site, constituting about activity, one in spring and one in autumn. The 71% of the total arachnofauna of the year, which adaptations of spiders to the bioclimatic season- is to be expected for insular, east Mediterranean, ality (being influenced basically by the day phryganic ecosystems (Bristowe, 1929; Herzog, length and/or temperature) are evident here, 1961; Moyano et al., 1986). On the other hand, reflecting the intensity of trophic interchanges Linyphiidae, a characteristic family of cold and of Mediterranean ecosystems during the period temperate climates, is the third commonest fam- from spring to autumn (Pearson & White, 1964; ily in the study area, being active only during the Iatrou & Stamou, 1989; Lamotte & Blandin, colder and moister season, i.e. in winter. 1989). Linyphiids also show high diversity in many A closer analysis of the patterns of different regions of southern Greece (Paraschi, 1988). families proves that the second peak in Gnaphosidae is the predominant family as far September is mainly produced by male mem- as both species richness and population densities bers of the families Gnaphosidae and Salticidae, are concerned. Mediterranean (Pterotricha thus the best adapted families into the area, lentiginosa), east Mediterranean (Nomisia sp.), whereas winter-active families form a totally or south European (Zelotes spp., Drassodes spp.) different pattern of activity, dominating the area species were the most abundant gnaphosids in only in the moist season. the study area. The dominance of Gnaphosidae The two-peak activity pattern, when present, indicates a diplochronous type of development. is to be expected in dry habitats as they are It may be explained either by the existence of equally represented in maquis or phrygana of two generations per year (Juberthie, 1954), or by insular and continental Greece (Paraschi, 1988). only one year-long adult period (assuming that Salticidae is represented by a good number of the pitfall traps are unable to record the full species (9) and great population densities when extent of the adult period, as the species are compared with most of the other families at the caught during their activity periods only) as pro- site. However, our data underestimate the con- posed by Toft (1976). As stated by the same tribution of Salticidae in the study area, when author, copulation may take place in the autumn compared with the 23 species found in the (as indicated by the large peak of males in maquis of the central Aegean (Paraschi, 1988). September), whereas egg development is post- This is probably because pitfall trapping alone is poned until late spring and summer, as indicated not an efficient method of sampling salticids by the peak of females in May–June–July, fol- (Merrett & Snazell, 1983). The data on the cen- lowed by a peak of immatures just afterwards tral Aegean spiders (Paraschi, 1988) were pro- (August). The smaller peak of males in spring is duced by pitfall trapping, quadrats, hand produced by males surviving the winter period. collecting, and other methods. This interpretation also accords with the opinion The presence of Ctenizidae is characteristic of of Tretzel (1954), that maxima of males indicate east Mediterranean habitats; Dysderidae also the period of copulation, whereas those of diversify greatly in many Greek regions, with female activity are connected with food- many endemic representatives, while Zodariidae capturing during the period of egg-development. are represented here by two species possibly However, if life cycles of species are not well new to science. Theridiidae are much less well known, no definite conclusions can be drawn represented on Mt Youchtas than in similar from the interpretation of pitfall data. ecosystems, where they can be considered as Finally, when possible groupings of the differ- dominant (Paraschi, 1988). This may be because ent microbiotopes based on the composition of pitfall traps collect only members that live in the spider families were checked, only slight prefer- litter, and not species from the vegetation above ences of some families towards a microbiotope (Merrett & Snazell, 1983). could be detected, even though the six 242 Proceedings of the 17th European Colloquium of Arachnology, Edinburgh 1997 microbiotopes were quite distinct. As stated by HEYDEMANN, B. 1961: Untersuchungen über die Merrett & Snazell (1983), this may be because Aktivitäts- und Besiedlungsdichte bei epigäischen pitfall trapping is unable to reflect differences Spinnen. Verh. dt. zool. Ges. 35: 538–556. among the higher strata of vegetation, thus pro- HUHTA, V. 1971: Succession in the spider communi- ducing a less clear grouping of sites. ties of the forest floor after clear-cutting and pre- scribed burning. Annls zool. fenn. 8: 483–542. IATROU, G. D. & STAMOU, G. P. 1989: Preliminary Acknowledgements studies on certain macroarthropod groups of a Quercus coccifera formation (Mediterranean-type We are very grateful to Dr K. Thaler for his ecosystem) with special reference to the diplopod help in the systematic part of this study. We also Glomeris balcanica. Pedobiologia 33: 301–306. wish to thank Mr S. Chatzimanolis for the sort- JUBERTHIE, C. 1954: Sur les cycles biologiques des ing and counting of the rest of the arthropods araignées. Bull. Soc. Hist. nat. Toulouse 89: trapped. 299–318. KULCZYN´SKI, W. 1903: Collected papers on spiders of Wl´adys´law Kulczyn´ski. Bull. Acad. Sci. References Cracovie 26: 32–58. LAMOTTE, M. & BLANDIN, P. 1989: Originalité et AITCHISON, C. W. 1984: The phenology of winter- diversité des écosystèmes mediterranéens ter- active spiders. J. Arachnol. 12: 249–271. restres. Biologia gallo-hellen. 16: 5–36. ASSI, F. 1983: Recherches écologiques sur le peuple- LUCAS, M. H. 1853: Essaie sur les animaux articules ment des araignées d’une garrigue du Liban. Thèse qui habitent l’île de Crète. Revue Mag. Zool. 5: Dr d’État, Université de Paris IV. 514–531. BIGOT, L. & BODOT, P. 1972: Contribution à ´LUCZAK, J. 1963: Differences in the structure of l’étude biocoenotique de la garrigue à Quercus communities of web spiders in one type of environ- coccifera. I. Étude descriptive de l’habitat et de la ment (young pine forest). Ekol. pol. 11: 159–221. faune des invertebrés inventoriés. Vie Milieu 23: MAGIORIS, S. 1991: Ecology of ground arthropods 23–43. of insular phryganic ecosystems and of a degraded BRIGNOLI, P. M. 1981: Vue d’ensemble sur les maquis ecosystem. Ph.D. thesis, University of araignées de Grèce (Araneae). Biologia gallo- Athens. hellen. 10: 161–169. MERRETT, P. & SNAZELL, R. 1983: A comparison BRISTOWE, W. S. 1929: The distribution and dis- of pitfall trapping and vacuum sampling for assess- persal of spiders. Proc. zool. Soc. Lond. 1929: ing spider faunas on heathland at Ashdown Forest, 633–657. south-east England. Bull. Br. arachnol. Soc. 6: BRISTOWE, W. S. 1934: The spiders of Greece and 1–13. the adjacent islands. Proc. zool. Soc. Lond. 1934: 733–788. MILNER, J. E. 1988: Oxleas Wood: Observations on BRULLÉ, A. 1832: Expédition scientifique de Morée. the spiders, their phenology and ecological strate- Tome III, 1e Partie: Zoologie; 2e Section: Des gies. Lond. Nat. 67: 97–118. animaux articulé. Paris. MOYANO, F. J., PASCUAL, F. & JIMÉNEZ, E. CHATZISARANTOS, C. 1940: Spiders of Attiki. 1986: Characterization of a spider community. Ph.D. thesis, University of Athens. I. Temporary and spatial distribution. In J. A. DI CASTRI, F. & VITALI-DI CASTRI, V. 1981: Soil Barrientos (ed.). Actas X Congreso Internacional fauna of Mediterranean-climate regions. In de Aracnología Jaca (España), I. Barcelona: Ecosystems of the world, 11. Amsterdam, Oxford, Instituto Pirenaico de Ecología (C.S.I.C.) and New York: Elsevier: 445–478. Grupo de Aracnología (Assoc. esp. Entomol.): 276. DUFFEY, E. 1962: A population study of spiders in MUMA, M. H. 1980: Comparison of ground-surface limestone grassland. J. anim. Ecol. 31: 571–599. spider populations in Pinyon-Juniper and arid- FASOLA, M. & MOGAVERO, F. 1995: Structure grassland associations in southwestern New and habitat use in a web-building spider commu- Mexico. Fla Ent. 63: 211–221. nity in northern Italy. Boll. Zool. 62: 159–166. PARASCHI, L. 1988: Study of spiders in maquis FOELIX, R. F. 1982: Biology of spiders. 1st ed. ecosystems of southern Greece. Ph.D. thesis, Cambridge, MA& London: Harvard University University of Athens. Press. PEARSON, R. G. & WHITE, E. 1964: Factors con- HERZOG, G. 1961: Zur Ökologie der terrestren tributing to the annual cycles of surface-active Spinnenfauna märkischen Kiefernheiden. Ent. Z., arthropods in moorland country. Entomologist’s Frankf. a. M. 71: 1–11. mon. Mag. 100: 201–206. Chatzaki et al.: Seasonal activity of Mediterranean ground spiders 243

PIELOU, E. C. 1984: The interpretation of ecological SOUTHWOOD, T. R. E. 1966: Ecological methods data. New York: Wiley. with particular reference to the study of insect POST, W. M. & RIECHERT, S. E. 1977: Initial inves- populations. London: Methuen & Co. tigation into the structure of spider communities. STRAND, E. 1916: Arachnologica varia XX. Spinnen J. anim. Ecol. 46: 729–749. und Opilionen aus Griechenland, Albanien und ROEWER, C. F. 1928: XI. Araneae. In Zoologische Kleinasien. Arch. Naturg. 82A: 158–167. Streifzuege in Attika, Morea und besonders auf der TOFT, S. 1976: Life-histories of spiders in a Danish beech wood. Natura Jutl. 19: 5–40. Insel Kreta. Abh. naturw. Ver. Bremen 27: 92–123. TRETZEL, E. 1954: Reife und Fortpflanzungszeit bei ROEWER, C. F. 1959: Die Araneae, Solifuga und Spinnen. Z. Morph. Ökol. Tiere 42: 634–691. Opiliones der Sammlunden des Herrn Dr. K. TURNBULL, A. L. 1973: Ecology of the true spiders Lindberg aus Griechenland, Creta, Anatolien, Iran (). A. Rev. Ent. 18: 305–348. und Indien. Göteborgs K. Vetensk.-o. vitterhSamh. UETZ, G. W. & UNZICKER, J. D. 1976: Pitfall trap- Handl. 8: 3–47. ping in ecological studies of wandering spiders. SOKAL, R. R. 1979: Testing statistical significance J. Arachnol. 3: 101–111. of geographic variation patterns. Syst. Zool. 28: WISE, D. H. 1993: Spiders in ecological webs. 227–232. Cambridge: Cambridge University Press.