Spider webs not uncommonly harbour a community of creatures that rely on the arachnids for food and board. The sprawling orbs of fully grown Nephila and the hanging tents of Cyrtophora often house a considerable population of moochers, minute globules of guanine with comb-footed limbs that devour the leftovers of a fatal arena or morsels too little for their landlady's liking. Some insects, too, have learnt to sidestep the dangers of sticky threads and even turn the tables on their would-be predators. Assaults from without come from wasps that hover before vertical orbs to snitch a treat or neotropical damselflies with the wingspan of small birds and the dexterity to pluck weavers from their webs.
Invasions of a more insidious nature are launched by reduviid bugs in the subfamily Emesinae, which are equipped with raptorial arms and spindly legs, the better to navigate the radial lines of their targets at a pace that probably escapes the notice of spiders they stalk. A possible precursor to this habit of hunting in another's den is evident in the occasional wont of more common assassins to test their treads on tightropes where easy pickings are held in suspended inanimation. But the Emesinae, in their trundle to stay abreast of an arthropological arms race, bear little resemblance to their broad-bodied cousins who prowl bark and leaf, having reduced their torsos to twig-like proportions and donning shades that extend the illusion of a walking stick. The business end of these bugs comprises a stout head bearing a foldable rostrum and a pair of, usually spiny, forelegs analogous to the armature of mantids. The remaining, considerably slender, appendages typically have well-developed claws with toothlike projections not unlike the tarsi of spiders and which similarly help the assassins avoid entanglement in foreign traps.
Some emesines lurk in the dense foliage of tree ferns and and lichen-covered trunks. Others prey on arthropods associated with birds' nests or leaf litter. A few species dwell in caves or behind the picture frames of old fashioned homes. Their pièce de résistance, however, is the ability to cohabit with spiders for months or more. Depending on how each scene plays out, the bugs might devour their hosts or be in turn outmanoeuvred and sucked dry. But many probably subsist on a diet of flies, gnats and wasps, with individuals sharing a web racing at a sloth's pace to reach each newly snared victim. At least seven species have been recorded from Singapore, but little else is known about these, often cryptic, hunters that offer little resistance to the naked eye searching for clarity in mirky woods.
It's also not certain if the spiders and their unruly housemates prey on the motley assemblies of flies that sometimes gather in unseeming numbers on webs, especially those in sheltered locations such as the deep cracks between the buttresses of large trees. Craneflies – which resemble giant, wiry mosquitoes – may dangle from a horizontal strand by their forelegs, singly or in pairs who appear to be courting disaster. Some gall midges also dance a fine line between risk and refuge, having the insurance policy of tenuously linked tarsal segments that easily separate should a toe get trapped in silk. Other than tipulids and cecidomyiids, fungus gnats in the family Mycetophilidae (to which the humped beast on the left likely belongs) are known to rest on hazardous nodes, where they appear immune to the onslaught of webslingers as well as the upwafts that threaten to rend these slight bodies against the wind and thrust them onto a highway to the heavens with no promises of a happily airever after.
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