biordinal
/bʌɪˈɔːdɪnl/ /bʌɪˈɔːd(ə)nl/adjective
Entomology. Of hooks on the prolegs of caterpillars: arranged in a straight line or circle, and of two different, alternating, lengths.
Origin
Mid 19th century (in an earlier sense). From bi- + ordinal.