Natural prey of the jumping spider Menemerus taeniatus ( Araneae : Salticidae )

The natural prey of the jumping spider Menemerus taeniatus (L. Koch, 1867) was studied on the Absheron Peninsula, Azerbaijan. The percentage of specimens of M. taeniatus found feeding was low (10.7%). This investigation showed that M. taeniatus is a polyphagous predator feeding on a wide range of arthropods, including representatives of eight arthropod orders. The primary food of M. taeniatus was Diptera and Lepidoptera, which collectively made up about two thirds of total prey. The length of prey killed by M. taeniatus ranged between 1.10 and 13.00 mm (mean 6.14 mm), which is between 15.2 and 216.7% (mean 90.3%) of the length of their captors. Most frequently taken prey (50%) were medium-sized arthropods varying between 50–100% of the spiders’ body length.

The present paper, deals with Menemerus taeniatus (L.Koch, 1867), and is part of a project on the prey of Palaearctic jumping spiders (Guseinov, 2004(Guseinov, , 2005;;Guseinov et al., 2004).M. taeniatus is a relatively large salticid (adult body length 8-10 mm), with adult males usually slightly smaller than adult females.It is a common Mediterranean species known from the Canary Islands and Morocco, throughout the Pyrenean Peninsula, from the Balkans to Azerbaijan, and in eastern Iran and the south-east of Israel (Weso owska, 1999;Proszynski, 2004).In Azerbaijan M. taeniatus occurs at low elevations, including semidesert, lowland steppe and submontane forest-steppe zone (Logunov & Guseinov, 2002), where it is found on cliffs, fences and outside walls of buildings (Guseinov, 2003).

MATERIAL AND METHODS
This investigation was carried out on the Absheron Peninsula, Azerbaijan.The study site was located near the village Gala.This is an open area of ephemeral semidesert covered with the dwarf shrubs, Artemisia fragrans Willd., and Alhagi pseudoalhagi (M.B.), and short grasses and herbaceous plants, predominantly Calendula persica C.A.M., Senecio vernalis Willd.& Kar., Medicago denticulata Willd., Erodium cicutarium (L.), Pterotheca marschalliana (Rchb.),Poa bulbosa L., Anisanthea rubens (L.) and Aegilops biuncialis Vis.A row of wooden electricity poles crossed the study area and M. taeniatus was found only on these poles.
Two surveys were conducted in 1998 (30 October and 6 November) and twelve in 1999 (from 13 April to 5 November), which took a total of 23.5 h.All surveys were carried out in daylight, between 11:00 and 17:00.During the surveys, poles were thoroughly searched for M. taeniatus, and the mouthparts of each individual found were inspected with a hand-lens (×4 magnification) to avoid overlooking small prey.Spiders with prey in their chelicerae were captured with a transparent cup, placed in separate vials containing 75% ethyl alcohol, and brought back to the laboratory where the prey was identified and the body lengths of both spider and prey measured.Spiders without prey were left in the field.At the same time, all spiders were classified as either: (1) adult males, which could be easily distinguished by their bicoloured (black and grey) palps (all other individuals of M. taeniatus have grey palps); (2) small juveniles, i.e., spiders less than 5 mm in length; or (3) large juveniles and females, specimens larger than 5 mm, with grey chelicerae.At each survey the numbers of spiders with and without prey were recorded separately for each of these categories.
Six M. taeniatus individuals dropped their prey before they could be captured.However, for four of them the lost prey items were clearly recognized as three moths and an ant.Thus, the dietary analysis is based on 60 prey items identified to at least the level of order.The prey belonged to eight orders of arthropods; seven from the class Insecta and one from the class Arachnida (Table 1).The dominant prey orders were Lepidoptera and Diptera, which collectively constituted about two thirds of the total prey (63.3%).All the Lepidopteran captured were adult moths.The most frequently caught were Psychidae (9 individuals), followed by Thyrididae (4), Gelechidae (3) and Eriocraniidae (1).It is likely that the lost moths also belonged to one of these groups.All Diptera were Brachyceran, represented by Tachinidae (11), Dolichopodidae (2), Therevidae (2), Syrphidae (1), Scathophagidae (1) and Otitidae (1).Spiders (Araneae) were the other order of prey and they accounted for over 10% of Fifty-six prey items were measured.Their length varied from 1.10-13.00mm (mean ± SD: 6.14 ± 2.86 mm), which was between 15.2 and 216.7% (90.3 ± 40.7%) of the length of their captors, which ranged from 2.50-9.50mm (6.87 ± 1.45 mm).The size distribution of the prey in relation to that of their captors is shown in Fig. 1.The most common were medium-sized arthropods (ranging in body length from 50 to 100% of that of the spider), and accounted for a half of the total prey measured (50.0%).Approximately one third of the prey of M. taeniatus (33.9%) consisted of large prey, which exceeded the length of the spider.Most of these did not exceed 150% of their captor's length and only three were larger.Small prey, less than half the length of the spider, were present in smaller proportions (16.1%).

DUSCUSSION
The percentage of M. taeniatus individuals found feeding was low (10.7%), which is typical of cursorial spiders (Nentwig, 1986;Nyffeler & Breene, 1990).It should be noted, however, that this value is high compared to that recorded for other jumping spiders (Jackson, 1977;Dean et al., 1987;Young, 1989).Another interesting fact is that males of M. taeniatus captured prey almost as frequently as females and immatures.This contrasts with the observations on other salticids (Jackson, 1977;Givens, 1978;Sathiamma et al., 1987), including congeneric Menemerus semilimbatus (Hahn, 1827) (Guseinov, 2004), in which males fed significantly less frequently than females.The reason for this difference is unclear.
This investigation indicates that M. taeniatus is a polyphagous predator feeding on a wide range of arthropods.Polyphagy is characteristic of jumping spiders (Nyffeler, 1999), with the exception of Portia fimbriata (Doleschall, 1859), which was observed to feed almost exclusively on spiders (Jackson & Blest, 1982;Clark & Jackson, 2000).The predominance of moths and flies in the diet of M. taeniatus is probably due to these insects frequently settling on wooden poles.Similarly, these two groups of insects accounted for about 70% of the prey of M. semilimbatus foraging on stone walls (Guseinov, 2004).However, in the diet of the latter species flies were significantly more abundant than moths.It is remarkable, that 86.7% of the prey of M. taeniatus consisted of winged insects, which is characteristic of jumping spiders that live above ground level, while epigeic salticids feed primarily on arthropods that crawl (Guseinov, 1999).Unlike some species of salticids, which specialise in catching dangerous prey such as worker ants or web-building spiders (Li & Jackson, 1996), M. taeniatus captured almost exclusively soft-bodied, "harmless" arthropods.All the ants caught by this species were either males or queens of Messor denticulatus.Unlike workers, reproductive individuals of ants are virtually defenceless and are easily caught by jumping spiders (Edwards et al., 1974).
The study of prey size preference in spiders has shown that most cursorial spiders, including salticids, do not catch prey that exceeds 150% of their own body length.The preferred prey length tends to be equal to or less than the length of the spider (Nentwig & Wissel, 1986).The findings reported here agree with this generalization.Most of the prey of M. taeniatus (ca.70%) were smaller than the spider, while those that were larger than their captors usually did not exceed 150% of the spider's length.
Prey of Menemerus taeniatus classified by order, number caught and percentage composition.

Fig. 1 .
Fig. 1.Number of prey in the different size categories (body lengths of prey expressed as percentages of the body length of their captors).