We describe for the first time immature stages of the Scymnus subgenus Neopullus; namely the egg, larval (4 instars), and pupal stages of Scymnus (Neopullus) sinuanodulus Yu and Yao (Coleoptera: Coccinellidae), which is indigenous to China. This lady beetle was imported to the USA for biological control of the hemlock wooly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), a serious pest of hemlocks in eastern North America. The egg's anterior pole has a rosette of 4–11 cup-shaped and 13–20 semi-circular structures that are likely micropyles. Unlike the subgenera Scymnus and Pullus, a Neopullus larva lacks a retinaculum on its mandibles but has, in common, the antennae with 3 distinct segments, the maxillary palpi with 3 segments, and the labial palpi with 2 segments. The pupa is naked with transparent viscous droplets on the tips of setae and the larval exuvium attached only to the last abdominal segment. We also annotate morphological development and behavior of feeding, oviposition, and defense. Both larvae and adults of this small lady beetle exhibit defensive reflex bleeding of orange viscous droplets: the larva from thoracic tubercles and the adult from the femorotibial joints.