Securiform: triangular-compressed; like the blade of a hatchet.

Sedentary: not active: settled or remaining in one place.

Segment: a ring or division bounded by incisions or sutures: a
segment of an insect or of any articulate is a transverse portion
reaching entirely across the body, originally separated on the exterior
by incisions or sutures from the preceding and the succeeding
segments, having attached to it not more than one pair of ventral
appendages, containing internally not more than one pair of nerve
ganglia which supply nerves to the pair of appendages; = somite,
arthromere: fusion of segments frequently obscures, as in the head:
externally the walls of one segment may be composed of a number of
sclerites separated from each other by secondary sutures.

Segmentate: made up of rings or segments.

Segmentation of egg: the division of the originally single celled egg into
a number of coherent cells or blastomeres; = cleavage.

Segregated: detached or scattered into groups.

Segregation: a separation or placing apart.

Sejunctus: separated.

Sellate: saddle-shaped.

Sematophore: a seminal packet, composed of the seminal fluid mixed
with the excretions of the accessory glands.

Sembling: = assembling; q.v.

Semen: the fluid secreted in the testes, containing the spermatozoa.

Semi-: half.

Semicircular: like the half of a circle.

Semi-complete: in metamorphosis, = incomplete; q.v.

Semicordate: half or partly heart-shaped.

Semicoronate: partly surrounded by a margin of spines, hooks or the
like.

Semicoronet: a margin of spines or hooks partly surrounding a
structure or process.

Semi-cylindrical: like a groove or half a cylinder.

Semi-hyaline: hyaline in part only: not altogether transparent.

Semi-looper: a caterpillar in which one or two pairs only of the
abdominal legs are wanting and where in progression, only small
loops are formed: see looper.

Semi-lunar: in the form of half a crescent.

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-metamorphosi