How about:The Daddy Longlegs will attempt to flee just after using her gas attack. In nature, the Daddy Longlegs has one other way to escape detection. She can hang from a web strand and rotate, or stand and vibrate, at so fast a rate that she becomes a near-invisible blur. In an AD&D adventure, characters seeking the Daddy Longlegs need to be very sharpsighted, or of the elven race, to detect a “spinning” spider, and then only if they are looking for it.
I'd say yes on Tremorsense based on that.Wikipedia said:Because their eyes cannot form images, they use their second pair of legs as antennae to explore their environment.
I'd say that the acid spray takes care of the scent glands. Do you think the spinning is justified for the harvestmen also based on this? Or should we give them some sort of distraction ability? Or just leave them as is?Wikipedia said:To deal with predators such as birds, mammals, amphibians, and spiders, some species glue debris onto their body, and many play dead when disturbed. Many species can detach their legs, which keep on moving to confuse predators, especially long-legged species vibrate their body ("bobbing"), probably also to confuse. This is similar to the behavior of the similar looking but unrelated daddy longlegs spider, which vibrates wildly in its web when touched. Scent glands emit substances that can deter larger predators, but are also effective against ants.