New proconiine leafhoppers (Hemiptera: Cicadellidae: Cicadellinae), associated with Chusquea bamboos and other tall grasses, are described from montane forests of Costa Rica: one species of Paraquichira n. gen. and two species of Quichira Young. The latter genus, previously known from only a male of the type species from western Panama, is redescribed with inclusion of female characters; a key to its species is provided. Oviposition into grass leaves was observed in captive females of P. costaricensis n. sp. and Q. tegminis Young. Females of both species powder their egg clusters with specialized brochosomes, stored in the form of spots on the female forewings. Unlike Quichira and several other Proconiini genera displaying this behavior, Paraquichira lacks the rakelike modification of the macrosetae on the female hind tibia. The shape of the female brochosomes, not previously used in cicadellid systematics, is included in the morphological descriptions. Also described are the immature stages of P. costaricensis n. sp. The younger instars seem to mimic jumping spiders, the similarity being enhanced by their unusual habit of holding the abdomen arched, which makes it seem shorter and more inflated in dorsal aspect. Affinities of the two genera are discussed based on their morphology and behavior.