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Sunday, 08 September 2019

Wasp spider

Argiope bruennichi (wasp spider) is a species of orb-web spider distributed throughout central Europe, northern Europe, north Africa, parts of Asia, the Azores archipelago, as well as recent sightings in North American states such as North Carolina and Ohio. Like many other members of the genus Argiope, (including St Andrew's Cross spiders), it shows striking yellow and black markings on its abdomen.
The spider builds a spiral orb web at dawn or dusk, commonly in long grass a little above ground level, taking it approximately an hour. The prominent zigzag shape called the stabilimentum, or web decoration, featured at the centre of the orb is of uncertain function, though it may be to attract insects.
When a prey item is first caught in the web, Argiope bruennichi will quickly immobilise its prey by wrapping it in silk. The prey is then bitten and then injected with a paralysing venom and a protein-dissolving enzyme.
The species Argiope bruennichi displays cannibalism when it comes to mating. We can see this because the sex ratio is so biased towards females later in the mating season. With so few females available, the males need to develop their own ways to potentially find and secure a successful mating like small size and proper time to find an immature female. The females, typically much larger in size when compared to the males, almost always consume their male counterpart after copulation. Males can often be seen in or near a female's web waiting for her to complete her final moult, at which time she reaches sexual maturity. At this time her chelicerae (jaws) will be soft for a short time and the male may mate with the female without the danger of being eaten. These males obviously want to avoid getting eaten and this is more or less the only time that they are able to take advantage. Although the cause for this type of dimorphism between sexes seems to have a much larger benefit for the females.

(latin: Argiope bruennichi)

 

Sunday, 08 September 2019