Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
2. lātesco, ĕre, v. inch. n. [2. latus], to grow broad, to widen (not ante-Aug.): napi non in ventrem latescunt, Col. 2, 10, 24: ossa paulatim latescentia, Cels. 8, 1: bis sex latescit fascia partes, Manil. 1, 680.