The fourth metatarsus of cribellate spiders bears a setal comb, the calamistrum, that sweeps over the cribellum, drawing fibrils from its spigots and helping to combine these with the capture thread's supporting fibers. In four uloborid species (Hyptiotes cavatus, Miagrammopes animotus, Octonoba sinensis, Uloborus glomosus), calamistrum length and cribellum width have similar developmental trajectories, despite being borne on different regions of the body. In contrast, developmental rates of metatarsus IV and its calamistrum differ within species and vary independently among species. Thus, the growth rates of metatarsus IV and the calamistrum are not coupled, freeing calamistrum length to track cribellum width and metatarsus IV length to respond to changes in such features as combing behavior and abdomen dimensions.