Semi-lunar valve: guards the auriculo-ventricular opening of the heart.
Seminal ducts: = vasa deferentia; q.v.
Seminal vesicles: enlarged tube or pouch-like structures which serve to store the seminal fluid of the male, and in which the later stages of its development may take place.
Seminiferous: semen-secreting.
Semipupa: that stage of the larva just preceding pupation: more specifically the interpolated stage between the active larva and the true pupa, in hyper-metamorphosis.
Semi-saggitate: like the longitudinal half of an arrow head.
Semitropical or Gulf strip: is the southern part of the Austro-riparian area extends from Texas to Southern Florida, covers a narrow strip in So. Georgia and probably follows the coastal lowlands into South Carolina.
Sensim: gradually.
Sensoria: the circular openings covered by membrane, on the antenna or legs of plant lice.
Sensory: relating to or having a sense function.