J. S. Rovner and S. J. Knost.
Post-immobilization Wrapping of Prey by Lycosid Spiders of the Herbaceous Stratum.
Psyche 81:398-414, 1974.

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POST-IMMOBILIZATION WRAPPING OF PREY
BY LYCOSID SPIDERS OF THE
HERBACEOUS STRATUM1
BY JEROME S. ROVNER AND SUSAN J. KNOST
Department df Zoology, Ohio University, Athens, Ohio 45701 The use of silk for wrapping prey is generally associated with those spiders that construct trapping webs; nevertheless, there are indications in the literature that wandering spiders sometimes use silk for this purpose. In some of the latter cases the silk is applied after the prey has been subdued by biting, a use corresponding to that of the diguetid and linyphiid web-weavers studied by Eberhard ( I 967). Post-immobilization wrapping in the latter two families was suggested to prevent the prey from falling out of the web during subsequent attacks (ibid.), and in araneid spiders to have the same and additional roles, depending on species and prey size (Robinson et al., 1969). The function of this behavior in the non-web-weaving ctenids (Melchers, 1963), theraphosids (Eberhard, 1967), and lycosids (Rovner, 1971) remained unknown and was the subject of the present study. Our findings suggested that post-immobilization wrapping by wandering spiders serves the same general function that it probably does in web-weavers- to prevent prey 'from dropping from the spider's elevated location down to the ground whenever it is released from the chelicerae during feeding, grooming, or subse- quent capture attempts.
METHODS
We observed individuals of Lycosa rabida Walckenaer (females = 12-19 mm), Lywsa punctulata Hentz (females = 13-15 mm), and Schizocosa crassipes (Walckenaer) (females = 8-10 mm) for the presence of and nature of prey wrapping. Whereas S. crassipes
was collected during spring on forest leaf litter, both species of Lycosa were found in grassy fields, L. rabida during the summer and L. punctulata during early fall. The spiders were collected in Athens Co., Ohio, USA.
Spiders were housed individually in plastic cages (70 X 125 X 70 mm high) with water available ad lib., and given mealworms (larvae of Tenebrio molitior) for maintenance feedings. Laboratory This study was supported in part by National Science Foundation Grant GB 35369 to J. S. Rovner.
.Manuscript received by the editor September 20, 1974.



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19741 Rovner & Knost - Wrapping of Prey 399 temperatures averaged 25.8 å 2.7å
( SD) over the entire investi-
gation.
Initial observations were made on spiders in boxes identical to their housing cages.
Each individual had been food-deprived for up to 7 days. In this phase of our study we used the following types of prey : terrestrial isopods ( ArmadiZlidium sp. ) , 6-8 mm ; Japanese beetles ( PopilZia japonica) , 10-12 mm ; mealworm larvae, I 8-20 rnm ; small grasshoppers (Cyrtacanthacridinae), 6-8 mm; small ground crickets (Nemobiinae), 10-13 mm; and vestigial-winged fruit flies (Drosophila melanogaster), 2 mm. We offered three prey at time = 0, and additional single prey at + 10 and +20 min (all of the same species) in most of these tests. (For fruit flies, groups of eight were added at each of the three times.) Observation periods were at least 30 min in duration. The spider then was returned to its home cage with its captured prey.
To determine the functions of the various spinnerets in wrapping, we sealed pairs of spinnerets with paraffin while female L. rabida were under C02 anesthesia. Two females underwent sealing of the anterior spinnerets; two had the anterior and median spinnerets sealed; and two, the median and posterior spinnerets. These spiders were subsequently observed and filmed (Bolex Macrozoom Super 8 mm camera, Model 160) during prey-wrapping. We also exam- ined the silk on the prey and substratum, after chasing away the female 'from her just-wrapped prey.
To study the preference of L. rabida (and, to some extent, L. punctulata) for the ground vs. the herbaceous stratum, we con- structed artificial "field habitats" in three terraria (0.2 X 0.4 X 0.2 m high). Cardboard "foliage" was fixed in a plaster base which provided the "ground surface" on % of the terrarium bottom. The remainder of the glass bottom was left uncovered to provide an alternative ground surface in case the plaster had a repellent effect on the spiders (which turned out not to be the case). Vertical and sloping surfaces projecting into space were provided by the artificial foliage (Fig. I). Spiders could climb to a height (limited by a glass lid) of 0.19 nl.
Three female L. rabida (tagged with non-toxic enamel) were housed in each terrarium. (Three individuals were cannibalized in the course of this experiment and were replaced with equivalently tagged substitutes.) To prevent possible conditioning effects, we fed the spiders on the ground as often as on the foliage. (Feeding was done at times other than the daily observation periods.) We observed the nine spiders for 2-hr blocks of time each day for 10 days during



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400 Psyche [September-December
Fig. 1. Female Lycosa rabi^a (with prey) on artificial foliage. the afternoon (on most days, 1300-1 500), and recorded the duration of time each spider spent on the ground vs. the foliage. At 5-hr intervals we also measured the height of those spiders that were on the foliage. After completing this phase of our study, we observed and filmed prey capture and wrapping by spiders on the artificial foliage. Analysis of these and other films was aided by use of a Bell & Howell Super 8 rnm Multi-motion projector. Field observations were made on L. rabida during daylight hours usually 1300-1 500), and during both day ( 1300-1 500) and night (2030-2200) conditions on L. punctulata. Tile spiders were detected at a distance and their location within the habitat noted. By ap- proaching carefully, we were able to film undisturbed L. rubida in the field.
Whereas individuals of 8, crassipes did not use silk after prey capture, those of L. rabid0 and, to a lesser extent, L. punctulata did so: In the latter two species, silk was not used to immobilize the prey, since wrapping began after the prey had ceased most of its struggling, usually several min after capture (Table I ) .



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19741 Rovner &f host - Wrapping of Prey 40 1 Table I.
Bouts of prey-wrapping by female Lycosa rabida (*) and Lycosa punctulata (t) when offered multiple prey during a 30-min period. A total of 12 spiders was tested on each type of prey. (Sample sizes in parentheses.)
Prey
- - - - - - - - -
Mean Mean Mean onset
Bouts/ revolutions/ duration after bite
captures bout (set) (min)
When beginning a bout of wrapping, the spider spread and wiggled its spinnerets, flexed its abdomen ventrad, and then pressed its anterior '
spinnerets to the substratum. (Sometimes additional attachment disks were placed on the substratum in this manner within an arc of 60' or less.) Then the spider began to pivot above the prey. In about 10% of the cases the spider pivoted % revolution (or
sometimes
revolution), fixed an attachment disk to the substratum, and then began to turn in the opposite direction. However, in most cases the spider pivoted in only one direction, while remaining cen- tered above the prey. During the first revolution, the silk was attached to the substratum at 2-5 points, the number perhaps de- pending on the prey's bulk. Fewer attachment disks were placed during the next turn or two, and usually only one or none during later revolutions.
During the first two or three turns, the spider usually held the prey in its chelicerae (Fig. 2). Consequently, as the spider revolved, the prey animals beneath it pivoted around with the spider. (Very large animals, while not held in the chelicerae during wrapping, and therefore not having their weight supported by the spider, were contacted by the palps, chelicerae, and sternum of the spider pivoting above.) If, as was the case with most prey, the spider held the prey in its chelicerae during early revolutions, it then released the prey during a subsequent turn and continued to pivot for one or more revolutions (Fig. 3). Throughout the process, the palps were used to contact or manipulate the prey. In L. rabida 80% of the wrapping bouts involved four or
fewer revolutions
(mean = 3.3 k 2. I SD ;
range = 1-14; n = 106). Some views of one such bout are sketched in Fig. 4.
All three pairs of spinnerets were used during prey-wrapping. Data obtained from experimental animals indicated the same roles



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402 Psyche [September-December
Fig. 2. Female liytosa rahida placing an attachment disk on the wb- stratum during the early phas; of prey-wrapping. The multiple prey are held in her chelicerae and palps.
Fig. 3.
Female Lyrosa rablda during the later phase of prey-wrapping. The prey have Just been released from her cheliceral grasp. (Her palps
continue to contact the prey.) Swathing silk issues from her posterior spinnerets.




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Rovner &f Knost - Wrapping of Prey
for the spinnerets in lycosids as in other spiders that wrap prey. When the anterior spinnerets were sealed, no attachment disks were produced.
The prey was wrapped but not fixed to the substratum. The same was true when the anterior and median spinnerets were sealed. When the median and posterior spinnerets were sealed, attachment
disks were fixed to the substratum and dragline laid around the prey, but no swathing silk.
In this case wrapping was
not effective. Multiple prey were not tied together; indeed, the prey items were often pushed apart by the legs of the pivoting spider. As the result of normal wrapping behavior, silk was placed around the bodies of the prey animals and attached to the substratum at intervals.
Although the pivoting spider had pulled the threads taut, thee silk was not dense enough to produce a very tightly wrapped package, as is produced by orb-weavers, for example. Indeed the wrapping was so sparse that it would be unnoticed by the casual observer. Nevertheless, thje prey group did form a more compact mass than it had prior to wrapping. When the spider resumed feed- ing, it lifted the prey away 'from the substratum a short distance (rather than lean down to feed) ; however, the lines running to the substratum generally remained intact due to their elasticity. After prey-wrapping, the spider sometimes groomed its chelicerae and palps, while remaining directly above the prey, and then resumed feeding. Additional prey that approached within reach were often captured; and one or more bouts of wrapping followed. However, regardless of whether further captures were made after the first bout of wrapping, subsequent bouts on the previously wrapped prey occurred later in the observation period in many cases. Table 11. Number of Lycosa rabida making single vs. multiple captures when offered multiple prey during a 30-min period (second figure) and the number of those captures in which wrapping occurred (first figure). Twelve
spiders of each sex were tested on each type of prey. Males
Females
Single Multiple Single Multiple
Prey capture capture capture capture
Isopods -/ Q --/O
Beetles
O/ 1 -/o
Mealworms o/ 9 -/o
Grasshoppers 2/ 7 2/2
Crickets
O/ 4 21'3
-
Totals 2/21 4/5 5/ 14 3 1/32




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Rovner &? Knost - Wrapping of Prey
L. rabida wrapped various types of prey, especially in situations in which multiple prey were captured (Table 11). While only 19% of the males captured multiple prey, 68% of the females did so. Considering both sexes together, wrapping occurred in 20% of the cases in which only single captures were made, and in 95% of the cases in which two or more prey were captured. Such correlations meant that females wrapped prey much more often than males, performing at least one bout of wrapping in 78% of the observation periods in which they captured prey (single or multiple), while males did so only 23% of the time. None of our spider species wrapped fruit flies.
As shown in Table I, individuals -of L. punctulata wrapped prey much less often than L. rab'ida and did so less intensively (fewer turns and shorter bout duration). Furthermore, it was only four of the twelve females that did so; none of the twelve males wrapped prey.
Field observations. -We watched penultimate and adult L. rabida on sunny, calm days (early July) in a grassy field near the edge of a woods. Undisturbed individuals rested motionless on the leaves and stems of grasses and other vegetation. The spiders typically were on horizontal or sloping surfaces (rather than vertical ones). Those individuals we happened to observe were on the upper leaves of relatively low vegetation or part-way up the stems and leaves of taller vegetation.
In response to mild disturbance, the spiders walked or climbed a short distance and then resumed their motionless stance. Strong disturbance (as that which resulted from our walking near them during our collecting 'efforts) caused the spiders to run and climb Fig. 4. [Opposite page]. Sketches, based on a Super 8 mm film, showing dorsal views of prey-wrapping by a female Lycosa rabida. The several items of the multiple prey-capture are drawn as an homogenous mass (stippled) for convenience, and should not be regarded as a wrapped bundle. Lighting conditions permitted seeing the silk in views B, E, and
G. Times were
rounded to the nearest sec. A. Placing 1st attachment disk (TimezO). B. One-quarter into the 1st revolution (+ 4 sec). C. Near end of 1st revolution
(+ 7 sec). D. One-third into 2nd revolution (+ 9 sec). E. Near end of 2nd revolution (+ 12 sec). Prey were released from, the chelicerae at the beginning of the next revolution. F. One-third into 3rd revolution (+ 14 sec). G. Beginning of 4th revolution (+ 18 sec). H. End of 4th and final revolution (+ 21 sec).



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406 Psyche [September-December
swiftly through the foliage, sometimes breaking into a series of leaps and dashes that carried them long distances along the top of low- growing vegetation in a few seconds. Thus, these animals usually remained in the herbaceous stratum; only occasionally did an in- dividual plunge downward and hide near the ground. Penultimate L. punctulata were seen in the fall in the same fields, and typically traveled through the herbaceous stratum when dis- turbed. At night these spiders were seen resting on or moving slowly upon the vegetation or, much less frequently, upon the ground. Laboratory studies. -The results of our study of diurnal stratum selection by undisturbed female L. rabida in an artificial habitat are summarized in Fig. 5. (Temperature was 25-26' and relative hu- midity > 60% throughout the 10 days.) During the 20-hr survey, the spiders were on the cardboard foliage 73% of the time. Most of that time the animals rested motionless on one of the "leaves" at an average height of 0.12 m, i.e., more than half-way up the "plant." The long axis of their bodies was usually in a plane ranging from nearly horizontal to a slope of about 60å from the horizontal. In the latter situation
the spider faced up- or downward. In those cases in which the spider rested vertically on a "stem" the spider 2 3 4 5 6 7 8 9
INDIVIDUAL
Fig. 5. Stratum selection by female Lycosa rabida in an artificial habitat. During 20 hr, spread over 10 days, we recorded the proportion of time spent on cardboard foliage (solid bar) vs. on the ground. At half- hr intervals within observation periods, we also measured the height .of those spiders that were on the foliage (hatched bar).



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19741 Rcwter & Knost.- Wrapping of Prey 407 typically faced downward. Individuals rested more often in an upright position on the upper surface of the leaf (illumination = approx. 400 lux) than they did in an inverted position beneath the leaf (illumination = approx. 130 lux).
We considered each spider's behavior within the 2-hr periods of observation and noted that each remained within the "herbaceous stratum" during the entire 2 hr in 5.3 (range = 4-7) of the ten periods. Each spider remained on the ground throughout the 2-hr period in only 1.6 (range= 0-3) of the ten periods. The spider moved from the ground to the foliage or vice versa in the remaining 3.1 (range = 2-4) of the ten periods.
Some observations made on- several female L, punctulata in the artificial habitat indicated that these spiders also tended to spend their time resting on the foliage. However, we did not quantify this part of our study.
After completing the 10-day survey of stratum selection by L. rabida, we observed and filmed prey-wrapping by these spiders on the artificial foliage. The behavior resembled that performed on the floors of the housing containers, as we described above. Wrapping Fig. 6.
Female Lycasa rabida wrapping prey on artificial foliage. This leaf sloped at an angle of about 60- to the horizontal.



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408 Psyche [Septem,ber-December
usually was performed at the capture site and therefore was carried out in all ~lanes, including the vertical. The spiders behaved on sloping leaves and vertical stems in a manner similar to that seen on the horizontal cage floors; however, pivoting was slower on the narrow surfaces, apparently due to the spider's having to seek foot- holds as it revolved "above" th~e prey (Fig. 6). In some cases, we intentionally disturbed the spider before or after prey-wrapping. In the former situation, the prey sometimes
was released from the chelicerae and dropped to a lower leaf or to the ground. On the other hand, if wrapping already had occurred, they prey did not 'fall from the capture site when released from the chelicerae, even on a vertical surface. When multiple prey were wrapped on a sloping surface, they:
( I) remained together rather
than roll apart and (2) hung at the wrapping site rather than drop to the ground, when the spider was chased away. A further bit of evidence for the adaptedness of L. rabida to the herbaceous stratum was provided later by the construction of a 'shelter web" (about 50 mm3) and, within it, an egg sac (infertile) by a female on a nearly horizontal leaf 0.13 m above the ground in the artificial habitat.
Preference for herbaceous stratum. -8. crassipes is well-known as an inhabitant o'f woodland leaf-litter (Kaston, 1948; Fitch, 1963) ; indeed, lycosids are generally regarded as ground-dwellers (Lowrie, 1968). However, L. rabida and L. punctulata can be collected by sweeping grass and shrubs (Kaston, I 948). Kuenzler ( I 958) also found L. rabida on the lower trunk ,and branches of trees in open woodland. Whitcomb et al. ( 1963) describe finding L. rabida in cotton fields on the ground during the day, but at night ". . . half- way up the cotton stalks feeding on bollworm or cabbage looper moths . . ." as well as on noctuid moths. At night, Eason and Whitcomb (1965) collected 80% of their specimens of L. rabida 2/3 rn or more above the ground in tall grass and bushes. According to Eason and Whitcomb (1965), "L. punctulata is mostly captured on or near the ground, since it has less tendency to climb into bushes than does L. rabida." While finding both species in grassland, Fitch
( I 963 ) reported that L. punctulata preferred '(. . . relatively open or barren situations as compared to L. rabida, which prefers a tall-grass habitat." Kaston (1948) stated simply that both species have the same habits.




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19741 Rovner &? Knost - Wrapping of Prey 409 Our field and laboratory observations are in agreement with the general idea expressed above - L. rabida and L. punctulata are adapted for spending a significant part of their life in the herbaceous stratum, rather than being, like most lycosids, ground-dwellers. (Obviously, stratum selection may vary during the life of an in- dividual under different conditions, both external (temperature, humidity, wind, etc.) and internal (hunger, sexual state, etc.) ). A difference between the species in regard to habitat or stratum selec- tion, suggested by some authors, was not examined by us, but might be revealed by quantitative field and laboratory studies. The rela- tively longer legs of L. rabida suggests a greater adaptation to the herbaceous stratum than that of L. punctulata, as does the stronger tendency of L. rabida to wrap prey.
While these lycosids are often seen running about, perhaps mi- grating from one habitat to another in response to micro-climatic conditions, or perhaps merely reacting to the collector's movements, most of their time is probably spent at rest on the foliage. This seemed to be the case in the field, and was certainly the situation in the artificial habitat. As has been noted elsewhere (Edgar, 1969), lycosid spiders generally remain motionless and wait for their prey to come within reach. Like the web-weaving spiders, the wandering spiders of the herbaceous stratum are resting on a medium that pro- vides effective transmission of vibrational cues from the prey. Function of prey-wrapping. - We hypothesize that post-immo- bilization prey-wrapping in L. rabida and L. punctulata is a be- havioral adaptation for life in the herbaceous stratum. It reduces the possibility of losing the prey items when the spider releases them from its cheliceral grasp between bouts of feeding. The spider may release its grasp to make an additional capture, to groom, to drink, or to locate another point on the prey's body for further feeding. Also, when startled by another animal or by shaking of the sub- stratum due to wind, the spider's momentary release of the prey would often result in its loss. No such problem exists for ground- dwelling forms.
Our hypothesis is supported by the absence of wrapping after the capture of small prey, which are easily held in the chelicerae and ingested in a relatively short time. It appears, then, that post-immo- bilization wrapping serves the same primary function in wandering spiders as it does in web-weavers - to prevent the prey from dropping to the ground from the spider's elevated location. Also, it is im- portant when multiple prey are captured by a wandering spider,



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410 Psyche [September-December
since the number of prey that the spider can hold in its chelicerae during feeding is limited.
As to the functions of the components olf prey-wrapping, we sug- gest the following. The swathing silk serves to enclose the prey, a role that is not only important for holding multiple prey together, but which is also of value in holding together the pieces that often result from the process of ingesting a single prey item. This latter function may be one reason for the occurrence of additional bouts of wrapping during the course olf feeding. The dragline may be entangled in the swathing band and serve to attach the prey package to the substratum via the attachment disks, although it seemed that the swathing band itself was connected to the attachment disks. Since attachment to the substratum seems to be of prime value in preventing loss of acquired food material, the re-anchoring that occurs in additional wrapping bouts during the course of feeding probably makes up for the breakage of lines that accompanies the physical and chemical processing of the prey by the feeding spider, and thus may be another reason for extra bouts of wrapping. The temporal pattern is one of providing multiple attachment points, along with swathing, during the early phase of each bout (while the prey is held in the chelicerae) and then devoting most of the remaining time to swathing (after the prey has been released from the chelicerae). The early phase (attachment) may be im- portant for effective wrapping, since it enables the spider to release