Nymphs are immature (young) stages of bed bugs. They grow by shedding their skin (molting), but they require a blood meal in order to molt. Bed Bugs have 5 nymphal stages, each slightly larger than the preceding one. Nymphs of all stages are smaller than the adult stage.
Newly hatched nymphs are only 1/16 inch long (1 mm) and they are about the size and shape of a sesame seed. These first stage nymphs are very pale and they appear to be almost clear until they feed on blood, then they become bright red.
Nymphs (2nd stage through 5th stage) vary widely in color from pale tan to brownish. They may have a reddish tinge soon after feeding on blood . Unlike bed bug adults, female and male nymphs do not have distinguishing external features.