Cucumber spider vanishes into beech leaves
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- Cucumber spider found in a fellow participant's hat during a forest bathing class in a beech grove, with a yellowish-green abdomen 5mm long and a conspicuous red mark below the spinnerets.
- Araniella cucurbitina was first described in 1757 by Swedish arachnologist Carl Alexander Clerck as Araneus cucurbitinus, then reassigned to its current genus in 1942, while Araniella opisthographa was originally described by Polish arachnologist Władysław Kulczyński in 1905 before being recognised as a distinct species.
- Five cucumber spider species occur in Britain, but only the two named above are common; they typically share habitat, are distinguishable only by microscopic examination of their genitalia, and are believed to hybridise on occasion.
- A sudden squally shower broke the forecast warm sunshine, soaking the group because the beech canopy was not yet in full leaf, before the class regrouped on a semi-circle of fallen trunks.
- The instructor directed the group to rough-stalked feather moss (Brachythecium rutabulum) cushioning the fallen trunks, and nettle and chamomile tea was passed around to warm participants.
- The spider's camouflage was compromised against the author's black fleece sleeve, but once returned to a low branch, its green body disappeared seamlessly into the beech foliage.
Why it matters: The encounter highlights how rarely two of Britain's cucumber spider species can be told apart in the field — even with the spider in hand, microscopic genitalia examination is the standard, and occasional hybridisation between A. cucurbitina and A. opisthographa complicates identification for both naturalists and arachnologists.
