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Long-horned Orb-weaver Spider (Macracantha arcuata, Araneidae)

This is the female. The males are diminutive in size and look completely different.
As members of the orb-weaver family of spiders, they build large circular webs in the forest understory. Despite their bizarre appearance, they are as docile and harmless as your garden-variety orb-weaver.
The purpose of the dramatic horns remains unstudied, but theories include: a demonstration of reproductive prowess; a difficult subject for predators to swallow; function as counterbalances so the spider can position itself securely in its web (similar to a tightrope walkers pole); and they are very effective at breaking up the spider’s body profile against a shadowy background of dappled vegetation and sky, rendering them invisible.
Several colour forms occur. This white morph occurs in southern China. Elsewhere in South-east Asia, they can be orange, red or all-black.

by Sinobug (itchydogimages) on Flickr.
Pu'er, Yunnan, China

See more Chinese spiders and arachnids on my Flickr site HERE

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sinobugPhoto

Beware the Serpent

A penultimate instar Paris Peacock Swallowtail Butterfly Caterpillar (Papilio paris, Papilionidae) deploys its defensive osmeterium.

The osmeterium is an eversible glandular organ positioned at the juncture of the head and thorax of Papilionidae immatures. When eversed in response to a threat, it produces a chemical odour shown to repel arthropod predators (ants, spiders, mantids). It seems logical to assume that, in conjunction with the serpent-like eyespots characteristic of final instars, the colouration and forked structure of the osmeterium rounds off the snake mimicry aimed at detering vertebrate threats.

Oddly enough, of the many many encounters I have had with Papilionid caterpillars, this has been the only time I have seen an osmeterium in use, albeit fleetingly, and this was the only capture. Personally (and proudly), I feel this may be partly because I don’t make a point of provoking or disturbing my subjects.

by Sinobug (itchydogimages) on Flickr.
Pu’er, Yunnan, China

See more Chinese caterpillars on my Flickr site HERE

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