Abstract: A serious invasive exotic mealybug pest, Phenacoccus solenopsis Tinsley, has been recently found in China, with a great potential threat to cotton production. In the laboratory, we studied the developmental duration, reproduction and morphology of the mealybug on cotton. The results showed that there are five stages (egg, 1st, 2nd and 3rd instar nymph and adult) in the life cycle of female, while in the male there are six stages (egg, 1st and 2nd instar nymph, pre-pupa, pupa and adult). The egg stage was short; the nymphal stage of the female lasted 15-20 days and the total life span of the female was about 47-59 days, while in the male the nymphal and pupal stage together lasted about 17-22 days and the total life span of the male was about 20-26 days. The longevity of the female was much longer than the male. P. solenopsis has strong fecundity with an egg laying amount per female adult ranging from 200 to 862 (average 458 eggs). Egg, elongate-oval in shape, orange in colour and slightly transparent. First instar nymph, yellowish green in colour, and moves very fast. Second instar nymph, the protuberances on marginal surface of body become visible, anal lobes protrudent; male and female can be differentiated by the dark spots on body surface in late-2nd instar stage. Third instar female nymph, similar to adult female, covered by a thin layer of white waxy powder, with dark dorsomedial bare spots on intersegmental areas of thorax and abdomen from 1st to 4th segment, these areas forming 1 pair of dark longitudinal lines on dorsum. Adult female, oval in shape, covered with a thick layer of white waxy powder; several pairs of dark spots present under the waxy powder on thorax and abdomen, with 18 pairs of lateral wax filaments, posterior 2-3 pairs longer. Male pupa covered in loose white silky cocoon. Adult male, small and blackish brown in colour; antennae long and thin; one pair of transparent fore wings with hind wings degenerated into poiser; and two pairs of abdominal filaments present at the terminal part of the body. The results of this study are the base for the further studies and sustainable control of this serious pest.

Key words: Phenacoccus solenopsis, cotton, developmental duration, reproduction, morphology