The Life-Cycle, Abundance and Seasonal Movement of the Wolf Spider, Lycosa (Pardosa) lugubris, in Central Scotland

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<ul><li><p>The Life-Cycle, Abundance and Seasonal Movement of the Wolf Spider, Lycosa (Pardosa)lugubris, in Central ScotlandAuthor(s): Walter D. EdgarSource: Journal of Animal Ecology, Vol. 40, No. 2 (Jun., 1971), pp. 303-322Published by: British Ecological SocietyStable URL: .Accessed: 07/05/2014 18:54</p><p>Your use of the JSTOR archive indicates your acceptance of the Terms &amp; Conditions of Use, available at .</p><p> .JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range ofcontent in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new formsof scholarship. For more information about JSTOR, please contact</p><p> .</p><p>British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal ofAnimal Ecology.</p><p> </p><p>This content downloaded from on Wed, 7 May 2014 18:54:54 PMAll use subject to JSTOR Terms and Conditions</p><p></p></li><li><p>303 </p><p>THE LIFE-CYCLE, ABUNDANCE AND SEASONAL MOVEMENT OF THE WOLF SPIDER, LYCOSA (PARDOSA) </p><p>LUGUBRIS, IN CENTRAL SCOTLAND </p><p>BY WALTER D. EDGAR </p><p>Department of Zoology, University of Glasgow </p><p>INTRODUCTION </p><p>Wolf spiders belong to the family Lycosidae, a group of ground-dwelling spiders which are among the largest and most conspicuous members of the terrestrial invertebrate fauna of temperate regions. Adult females of the European representatives of the genus Lycosa are about 6 mm in length. Lycosids have relatively good eyesight, by spider standards (Homann 1931) they are good sprinters and they do not make use of silk to catch their prey. They are said to chase and catch their prey (Savory 1928; Nielsen 1932; Bristowe 1958) although this has been questioned (Edgar 1969). The egg mass is wrapped in a layer of silk and this cocoon or egg sac is carried by the female, attached to her spinnerets. Their large size, conspicuousness and high density in favourable habitats, makes them very suitable for population studies. </p><p>The wolf spider, Lycosa lugubris (Walckenaer), occurs over the whole of Western Europe, from Finland in the north to Spain and Italy in the south. It is found in Asiatic as well as European Russia (Bristowe 1939), and has also been recorded in Japan (Yagi- numa 1962). Most authors describe its habitat as being in or near woods (Dahl 1908; Norgaard 1945; Locket &amp; Millidge 1951; Wiebes 1959; Hallander 1967a). Locket &amp; Millidge say 'it never seems to occur far from woods' while Wiebes says it is 'very com- mon in clearings in woods'. All the specimens of L. lugubris which I have taken in Scot- land have been collected in or near deciduous woodland. </p><p>This paper, which is part of a 4-year study on the ecology of L. lugubris, attempts to elucidate the close association of this spider with woodlands. This has been done by studying the life-cycle, and the habitats occupied by the spider at different stages in its life-cycle. </p><p>Most of the field work was carried out in an oak woodland (Quercus petraea (Matt.)) near Glasgow University Field Station on the Ross Peninsula on the east bank of Loch Lomond. The average height of the trees was between 40 and 50 ft and they were 70-100 years old. Clearings had been made in a number of areas to allow for the planting of conifers. Vaccinium myrtillus L. is the dominant plant over large areas of the Peninsula while Pteridium aquilinum (L.) is dominant in places. </p><p>In this paper frequent reference is made to whether the sampling areas are shaded or whether they are situated in clearings. Reference is made to eight sampling areas. Areas I and 2 were partly shaded, areas 3-6 were shaded and areas 7 and 8 were in clearings. The following is an account of the vegetation at a site which included three of the largest sampling areas. Two of these (areas 7 and 8) were located in a clearing and one (area 6) in a shaded area. The vegetation at this site, which consisted of a stand of oak trees and adjacent clearing, was fairly typical of that found in all the sampling areas. </p><p>The nature of the vegetation, in the clearing in which areas 7 and 8 were situated, is </p><p>This content downloaded from on Wed, 7 May 2014 18:54:54 PMAll use subject to JSTOR Terms and Conditions</p><p></p></li><li><p>304 Life-cycle and seasonal movement of Lycosa lugubris </p><p>indicated in Plate 6(a); and that in the shaded area, in which area 6 was located, in Plate 6(b). The clearing was an area of acid grassland dominated by Deschampsiaflexuosa (L.). It was species-poor and had little vertical layering. There was a fairly dense mat of Galium saxatile L. and several clumps of bracken (Pteridium aquilinium). Also present were Thelypteris limbosperma (All.), Oxalis acetosella L. and Luzula pilosa L. The most abund- ant mosses were Hylocomium splendens B and S., Pseudoscleropodium purum (Hedw.) and Pleurozium schreberi (Brid.). In the shaded area the bracken was much more dense and there was a considerable amount of leaf litter. Other ferns present included Blechnum spicant (L.) and Thelypteris limbosperma. The grass was much less dense than in the clear- ing and consisted of Deschampsiaflexuosa, Agrostis canina L. and a few clumps of Molinia caerulea (L.). Bluebells (Campanula rotundifolia L.) were fairly abundant and the more important mosses present were Polytrichum species and Hypnum cupressiforme Hedw. </p><p>Mid-winter </p><p>Dead bracken Area 6 </p><p>stms /Leaef Are 7 Log9\L </p><p>stems\ ~~~~~~~~litter </p><p>Mid-summer </p><p>Short i3 - Area 6 Bracker dense </p><p>Area 7 grass Log </p><p>FIG. 1. Diagrammatic representation of the locality in which sampling areas 6 and 7 werQ situated, in winter and suummer. </p><p>As will be seen later, the seasonal changes in the vegetation were considered to be important with regard to the seasonal distribution of Lycosa lugubris. These changes were particularly striking with respect to the state of the oak trees and the bracken. A dia- grammatic representation of areas 6 and 7, in mid-winter and in mid-summer, is given in Fig. 1. As the trees and most of the bracken were present in area 6, the seasonal vegetation changes were more striking in this area than in area 7. In mid-winter there were large accumulations of leaf litter and dead bracken stems in area 6. The dead bracken stems served to bind the leaf litter and thus prevented the dead leaves from being blown away. Towards the end of April the young bracken stems appeared. In mid-May the oak trees broke their leaves and these exerted their full shading effect by the end of May. By early </p><p>This content downloaded from on Wed, 7 May 2014 18:54:54 PMAll use subject to JSTOR Terms and Conditions</p><p></p></li><li><p>Journal of Animal Ecology Volume 40, Plate 6 </p><p>e-~~~~~~~~~~J N </p><p>(a) Vegetation in clearing in summer. (b) Vegetation in shaded area in summer. (Photo- graphs by W. D. Edgar.) </p><p>(Facing p. 304) </p><p>This content downloaded from on Wed, 7 May 2014 18:54:54 PMAll use subject to JSTOR Terms and Conditions</p><p></p></li><li><p>WALTER D. EDGAR 305 </p><p>August the bracken was about 1 m in height. It started to die off in autumn and in late autumn and early winter the oak trees shed their leaves. </p><p>THE LIFE-CYCLE OF LYCOSA LUGUBRIS </p><p>The life-cycle of Lycosa lugubris is illustrated in Figs. 2 and 3. The information on which this account is based was collected during the course of an investigation on density, </p><p>}Oinuary </p><p>July </p><p>FIG. 2. The life-cycle of Lycosa lugubris. Closed areas, second instar-sub-adult; stippled areas, sub-adult; hatched areas, adult male; open areas, adult female. </p><p>Sub-adult males </p><p>Sub-adult females Adult males </p><p>Adult females </p><p>Egg sacs carried Spiderlings emerge </p><p>Most females Most females carrying egg sacs carrying egg sacs </p><p>Significant events First matings Most males Females start observed have died to die </p><p>I I A </p><p>I i I i I </p><p>A II M A M J J A S 0 </p><p>FIG. 3. Phenology of the adult stage of the life-cycle of Lycosa lugubris. </p><p>natality, mortality and growth rates of L. lugubris. Density estimates were obtained using the Lincoln Index (Lincoln 1930) and by quadrat sampling (see later). Natality was esti- mated by counting the numbers of eggs in the egg sacs, and growth rates were obtained by taking representative samples of the spiders, at regular intervals, and weighing the ani- </p><p>This content downloaded from on Wed, 7 May 2014 18:54:54 PMAll use subject to JSTOR Terms and Conditions</p><p></p></li><li><p>306 Life-cycle and seasonal movement of Lycosa lugubris </p><p>mals in these samples. The results of the investigation on mortality, natality and growth rates of L. lugubris are reported elsewhere (Edgar 1971). </p><p>Females of L. lugubris normally produce two egg sacs during their life. The spiderlings from the first egg sac emerge about the middle of July; those from the second about mid- September. By the time they are ready to overwinter the majority of these spiderlings have reached the fourth instar stage, some are third or fifth instars while a few are in their second instar. The fifth and most of the fourth instars are products of the first egg sac. They overwinter in the leaf litter and during the following spring and summer continue their development so that by the beginning of September most are sub-adult, i.e. at the next moult they become adult. These sub-adults overwinter for a second time in the leaf litter. </p><p>On mild sunny days during the winter a few sub-adults can be found but they do not become generally active until early March. The first adult males appear in late March, and early in April adult females can be found. Under field conditions males are considered to be adult in instar eight and females in instar nine (Edgar unpublished). Most of the sub-adults become adult by the end of April at which time the first mating pairs can be found. By the middle of May the first females carrying egg sacs are present and by the end of May most females have egg sacs. These are carried for 5-6 weeks before the female tears open the egg sac to allow the spiderlings to emerge. In Fig. 2 the period of carrying the first egg sac is indicated as covering a period of 11 weeks. This is the total period of time when females carrying first egg sacs can be found and not the time that individual spiders carry their egg sacs. The spiderlings climb on to their mother's back and are carried in this fashion for up to a week before dispersing. Most of the males have died by late June; the females retain the spermatozoa from the spring matings to fertilize the second egg sac (Vlijm, Kessler &amp; Richter 1963). By mid-August most of the females are carrying a second egg sac and the spiderlings from this egg sac emerge about the middle of Septem- ber. By the end of September the females beging to die and by the end of October few adult females can be found. Thus the females live, on average, just over 2 years, while the males live for just under 2 years. </p><p>SEASONAL MOVEMENT OF LYCOSA LUGUBRIS AND ITS EFFECT ON DENSITY ESTIMATES OF ADULT AND SUB-ADULT ANIMALS </p><p>The distribution of L. lugubris in the oak woodland of the Ross Peninsula was markedly discontinuous. In March 1965, sampling areas were selected in localities where L. lugubris was abundant. Due to the discontinuous distribution mentioned above, most of the sam- pling areas were relatively small, e.g. 5 5 x 5 5 m. In early March the sub-adult animals were still in overwintering areas. The spiders overwintered in leaf litter hence the sampling areas had large accumulations of leaf litter, being situated beneath oak trees. </p><p>A simple Lincoln Index method (Lincoln 1930) was used to obtained density values for sub-adult and adult animals. Density estimates of the smaller instars were obtained by quadrat sampling and these will be discussed separately. </p><p>Spiders were collected by hand by proceeding round the perimeter of the area and gradually working inwards. This was called the initial capture and the type of sampling was termed 'systematic sampling'. The spiders were brought back to the laboratory, anaesthetized with carbon dioxide, placed on their backs under a binocular microscope and marked on the sternum and underside of the coxae with Humbrol 1-h enamel paint. A marking code was used such that females carrying egg sacs, females with spiderlings </p><p>This content downloaded from on Wed, 7 May 2014 18:54:54 PMAll use subject to JSTOR Terms and Conditions</p><p></p></li><li><p>WALTER D. EDGAR 307 </p><p>and females without egg sacs or spiderlings, were distinguished. The spiders were retained overnight to allow the paint to dry and were then released in the sampling area from which they had been taken. After a suitable release period, experience showed 1 day to be the most appropriate (Fig. 4), a second collection was made in the same area, and the number of marked and unmarked spiders recorded. The total population in the area was calculated using the formula: </p><p>an r </p><p>where P = total population, n = total number of individuals in second sample, a total number marked, r = total recaptures. </p><p>40 </p><p>35 - * n=28\ ~10 </p><p>-, 30 - </p><p>0.- n=7 O25 n=3 </p><p>* 20 </p><p>a) 15 n=3 1 5 </p><p>E * o n= \ </p><p>0= \ </p><p>5 </p><p>l , ,I, ,1 ,_ 1 , I , ,1 1 ,I 1 2 3 4 5 6 7 8 9 10 </p><p>Duration of release period (days) </p><p>FIG. 4. Relation between percentage of marked specimens of Lycosa lugubris recaptured, in mark and recapture experiments, and the duration of the release period. (The regression line was calculated using all the fifty-six observations, but only the mean values are plotted: </p><p>n = number of observations from which mean value was calculated.) </p><p>The release period was in all cases 24 h or more and it was considered that so long as the marked animals were left overnight in the field they would be mixed at random with the rest of the population. The high percentage of marked animals recaptured, when the release period was short (1 or 2 days) (Fig. 4), suggests that the movement of marked animals out of the area during the release period was not too important a source of error. Marked spiders, kept in the laboratory for several months, retained their marks well and showed no ill-effects from having been marked. Marked animals were recovered in the field, several months after marking, with their marks still clearly visible and several spiders marked in the autumn were recovered the following spring. Thus the marks would also seem to be retained in the field. Anaesthetizing has been shown to have a detrimental effect on certain arthropods (Southwood 1966) and Hallander (...</p></li></ul>