Spiders

Araneae

Spiders belong to the order Araneidae (Aranae). As in mites, the prosome is made up of the head and thorax fused together and carrying the four pairs of legs made up of 7 sections. Up to 8 single eyes are inserted on the prosome as well as pedipalps used for handling prey (photos 1 and 2). Spiders, which consume only live prey, do not have grinding mouthparts. They inject through the chelicerae (or hooks), placed near the mouth opening, venom to immobilize their prey as well as digestive enzymes which will liquefy it and which they will then suck.

The second part of the body is the abdomen or opisthosome. Sericogenic glands located on the abdomen produce silk (photo 3), a protein that solidifies in air and made up of microfibrils and which makes it possible to form webs or to wrap them directly. Silk is also used for the formation of nests protecting the eggs (photo 4).

Spiders catch their prey directly (hunting with hounds or on the lookout), or using webs or silk threads. These predators are generalists and consume all kinds of prey and thus spiders are considered to regulate, to a certain extent, the populations of insect pests in the vineyard.

• Biological cycle

The life cycle of spiders in our latitudes evolves over one to two years, but some species have two generations per year. The duration of development, for a given species, depends on the environment (climate, food). The eggs, protected by the cocoon, hatch giving young which resemble adults (photo 5). From gregarious, they then become solitary. Because of the exoskeleton, the molts (photo 6) allow the spider to grow bigger, and when it reaches the adult stage, it stops molting.

• The species of the vineyard

Vineyard spiders form tolerant stands that are not specific to anthropized environments but originate from open natural environments that surround the vineyard, these arthropods inhabiting the herbaceous layer and then the foliage after bud break. According to the few studies carried out, there are no specific species in the vineyard. Composed of ubiquitous species, the populations are very diverse. Thus, in Beaujolais, we have observed 60 different species of spiders belonging to 17 families, 13 families in Languedoc-Roussillon, and in Switzerland up to 130 different species.

• The most frequent families in the vineyard

- Salticidae , or jumping spiders. A fairly easy family to recognize, these relatively small spiders are wanderers in the foliage of grapeviness that hunt by sight and capture their prey by jumping on them, they usually do not build webs (photos 7 and 8). These spiders hunt on the ground or in vegetation.

- Lycosidae , or wolf spiders. The members of this family hunt on the ground, by stalking or in ambush. These spiders have 8 eyes arranged in three rows, the females carry the cocoon sheltering the eggs on them (photo 4) as well as the young after hatching until they disperse. very frequently observed Pardosa is in the vineyard in spring.

- Araneidae , a large family of weavers of more or less circular webs. Drops of glue are arranged on the wires to secure the prey before being packed by the spider. The large Argiope bruennichi builds a stabilimentum, an area where the weaving is tighter. Araneus diadematus and Araniella cucurbitina are frequently observed species (photo 9). Nuctenea umbratica has a nocturnal activity.

- Thomisidae , or crab spiders hunting on the lookout. These spiders can be recognized by their two pairs of very developed front legs (photo 1). In this family, Misumena vatia stands out particularly in flowers and its coloring varies depending on the medium in which it stands. Synema globosum , a very common species in the vineyard, is characterized by strong sexual dimorphism (photo 10). This species lays its eggs in a cocoon woven into a folded leaf.

- Theridiidae ; these spiders weave an irregular web in a tablecloth. They have thin legs and an easily recognizable protruding abdomen (photo 11).

Many other families can be found in the vineyard, Linyphiidae, Erigonidae, Gnaphosidae (photo 12), Dysderidae, etc. Some tiny linyphids hunt low to the ground on small, irregular webs and appear to resist cultural practices.

• Biological regulation

Spiders fall prey to various predators, such as birds, lizards, some rodents, etc. and among the insects the Pompilidae (Hymenoptera apocrites Vespoidea) and Sceliphron (Hymenoptera apocrites Apoidea). These insects paralyze their prey before taking them away. After laying, these preys will be used to feed the larvae.

Bibliography

Emerit M. (2011) Spiders. In: Auxiliary fauna of the vineyards of France, Eds France Agricole-Dunod

SEBIOREF project (2017) Knowing the biodiversity useful to agriculture to reason its practices - Sheet 3: Spiders .