Cribellum and calamistrum ontogeny in the spider family uloboridae: Linking functionally related but separate silk spinning features

The fourth metatarsus of cribellate spiders bears a setal comb, the calamis trum, that sweeps over the cribellum, drawing fibrils from its spigots and helping to combine these with the capture thread's supporting fibers. In fo ur uloborid species (Hyptiotes cavatus, Miagrammopes animotus, Octonoba sin ensis, Uloborus glomosus), calamistrum length and cribellum width have simi lar developmental trajectories, despite being borne on different regions of the body. In contrast, developmental rates of metatarsus IV and its calami strum, differ within species and vary independently among species. Thus, th e growth rates of metatarsus IV and the calamistrum are not coupled, freein g calamistrum length to track cribellum width and metatarsus IV length to r espond to changes in such features as combing behavior and abdomen dimensio ns.