Alleged silk spigots on tarantula feet: electron microscopy reveals sensory innervation, no silk.

Several studies on tarantulas have claimed that their tarsi could secrete fine silk threads which would provide additional safety lines for maintaining a secure foot-hold on smooth vertical surfaces. This interpretation was seriously questioned by behavioral experiments, and more recently morphological evidence indicated that the alleged spigots ("ribbed hairs") were not secretory but most likely sensory hairs (chemoreceptors). However, since fine structural studies were lacking, the sensory nature was not proven convincingly.

Silk secretion from tarantula feet revisited: alleged spigots are probably chemoreceptors.

Controversial views have been expressed about whether tarantula feet can secrete fine silk threads that could prevent them from falling off smooth vertical surfaces. Two studies have claimed that 'ribbed hairs' on the tarsi of tarantulas produce silk. We examined these ribbed hairs in several tarantula species using light and scanning electron microscopy, and compared them with the silk-producing spigots on the abdominal spinnerets.

Peripheral synapses and giant neurons in whip spiders.

Among invertebrates the synapses between neurons are generally restricted to ganglia, i.e., to the central nervous system (CNS).