Key to species of Metapenaeus in Taiwan

1. Rostrum with distinct basal crest and failed to reach distal segment of antennular peduncle.................. M. tenuipes

-. Rostrum without distinct basal crest and more or less extending to tip of antennular peduncle......................... 2

2. Telson with 3 pairs of large movable spines..................................................... M. intermedius

-. Telson without distinct movable spines.................................................................... 3

3. Rostrum unarmed at distal 1/3; males with basial spine of the pereiopod III extremely long and barbed......... M. joyneri

-. Rostrum armed with teeth along entire dorsal border; males with basial spine of pereiopod III not elongated and simple.... 4

4. Males with basal notch at merus of pereiopod V accompanied by a spiniform process and row of tubercles, petasma with distomedian projections very large and greatly swallow, triangular or subquadrate in shape; female thelycum with posterolateral edges of lateral plates highly elevated and strongly recurved inward....................................... M. ensis

-. Males with basal notch at merus of pereiopod V only accompanied with a large tubercle, petasma with distomedian projections flap-like or reduced; female thelycum with margins of lateral plates flattened or if raised, not strongly curved inwards..... 5

5. Male petasma with distomedian and distolateral projections more or less extending to same level; female thelycum with lateral plates having lateral margins raised as ridges....................................................... M. elegans

-. Male petasma with distomedian projections considerably overreaching or falling short of distolateral projections; female thelycum with lateral plates having lateral margins not ridged...................................................... 6

6. Male petasma with distomedian projections very large and extending far beyond distolateral projections; female thelycum with anterior margin of anterior plate convex and bearing 3 tubercles, lateral plates with median longitudinal furrow.. M. moyebi

-. Male petasma with distomedian projections reduced, very low and far from tips of distolateral projections; female thelycum with anterior margin of anterior plate straight or concave, without tubercles, lateral plates lacking median longitudinal furrow............................................................................................ M. affinis