Makin’ do with less

The paucity of photons at night poses special problems for small nocturnal ambush predators, at least if vision is the principal sensory modality. All spiders are carnivores and must snare their prey with stealth or traps. Most arachnid predators that rely on vision and stealth, such as salticids (British Journal of Ophthalmology, March 2006), are almost exclusively diurnal. These spiders have evolved large, anterior median eyes among their four sets of eyes. But, sharp-eyed nocturnal arachnid predators, such as the lycosids (British Journal of Ophthalmology, November 2002), have evolved large posterior median eyes, but why the difference?

Deinopis subrufa has an interesting lifestyle, as the common name, net-casting spider, suggests. Spread through the remnants of the ancient Gondwanaland, D subrufa spins a cribellate (a sticky form of silk different from that spun by orbweavers) web and uses it as a trap. The spider holds the web with four of its eight legs and hides under vegetation. She will often dangle, head down, under a leaf, her long body and legs resembling a stick. She will hang just above ground level and prepare the trap. From that position, she will defecate …