*COMMENT ~ Orders: Character notes. 
 
*CHARACTER NOTES 
#1. ~ (alternatively) is here used to indicate sometimes not
unreasonably included in or reduced to. 
#4. Lengths, recorded for adults, are measured from the front of the
carapace (exclusive of appendages) to the posterior end of the abdomen. 
#6-7. The males of a species generally have relatively longer legs and a
narrower abdomen than the females. 
#10-13. The eyes of spiders (usually 8, sometimes 6) take the form of
simple ocelli. Much classificatory interest and identificatory
convenience attaches to their patterns of insertion, and to their
relative sizes. For comparative descriptive purposes, they are
classified (presumably according to supposed homologies, and with
reference to 8-eyed forms) as follows:- \par{}2 anterior medians (front
middle: AME); 2 front anterior laterals (front outside: ALE); 2
posterior medians (back middle: PME); and 2 posterior laterals (back
outside: PLE). \par{}This terminology involves interpreting the various
patterns as basically representing two horizonatal rows, anterior and
posterior. The eye patterns of 6-eyed spiders (\i{}Dysderidae\i0{},
\i{}Oonopidae\i0{}, \i{}Scytotidae\i0{} and \i{}Segestriidae\i0{}) are
not overtly interpretable in such terms; and while they are readily
applicable to the eye layouts of most 8-eyed spiders, several 8-eyed
families are characteristically anomalous (see the accompanying
illustrations, which should be cross-referenced with the diagrams
available via the General morphology toolbar button). 
#15-16. \i{}Chelicerae\i0{} (sing. \i{}chelicera\i0{}): the jaws of the
spider, representing the first pair of organs of the cephalothorax. Each
comprises a large basal part and a fang. The latter, which represents a
claw-like distal segment, bears near its tip the opening of the duct
from the poison gland. 
#18-20. \i{}Palpi\i0{} (palps, pedipalps): the second pair of appendages
of the cephalothorax, located behind the chelicerae (q.v.) and in front
of the first pair of legs. By comparison with the legs (q.v.), they
exhibit coxa, femur, patella, tibia and tarsus, but lack the metatarsus.
The coxae of the palps constitute the \i{}maxillae\i0{}; i.e., the
spiders palps are homologous with the maxillary palps of insects. The
palps of male spiders are modified - often greatly so - for sperm
transfer. \par{}The palpal organ of the male spider is attached to the
terminal segment of the palp, which represents the tarsus. The latter is
commonly broadened and hollowed to receive it, and is then termed the
\i{}cymbium\i0{}. The cymbium in some families bears a small branch,
hook or knob, or a separate sclerite attached to it by a membrane, which
is termed the \i{}paracymbium\i0{}. \par{}A male palp varies greatly in
appearance, depending on the direction from which it is viewed (dorsal,
ventral, inner side, or outer side). Except where stated otherwise,
Blackwall's illustrations represent ventral (underside) views of left
palps, and the palpal organs are depicted in their normal, unexpanded
state. Males that have recently moulted are usually lighter and less
sclerotized; and in sub-adults the palpal tarsi, though usually somewhat
swollen, can be expected to lack the complex arrangements of sclerites
characterizing the adults. \par{}\par{}\i{}Mature male spiders\i0{} are
readily recognised by their pedipalps, which are complex in structure.
In addition, the usually relatively small and slim male abdomen never
exhibits an epigyne. \i{}Mature female\i0{}s have simple pedipalps
(though rarely they are distally expanded), and the relatively large and
plump abdomen usually exhibits an epigyne. \i{}Immature spiders\i0{}
inevitably pose problems for identification. They have modified palps
and no epigyne, and are often pale (sometimes almost translucent) and of
relatively fragile appearance. 
#28. \i{}Calamistrum\i0{}: a longitudinal series of curved bristles, on
the dorsal edge of the metatarsus of the fourth leg in some families. It
is used to comb out a viscid secretion extruded by the cribellum (q.v.),
which combines with the ordinary threads to form an adhesive, faintly
bluish, hackled (lace-like) web. \par{}\par{}\i{}Mature male
spiders\i0{} are readily recognised by their pedipalps, which are
complex in structure. In addition, the usually relatively small and slim
male abdomen never exhibits an epigyne. \i{}Mature female\i0{}s have
simple pedipalps (though rarely they are distally expanded), and the
relatively large and plump abdomen usually exhibits an epigyne.
\i{}Immature spiders\i0{} inevitably pose problems for identification.
They have modified palps and no epigyne, and are often pale (sometimes
almost translucent) and of relatively fragile appearance. 
#45. \i{}Cribellum\i0{}: a spinning organ, in the form of a transverse
plate, found immediately in front of the spinnerets in some families. It
is covered with minute spigots, secreting a viscid substance which,
combined with the normal threads by use of the calamistrum (q.v.), forms
adhesive, faintly bluish, hackled (lace-like) web.
\par{}\par{}\i{}Mature male spiders\i0{} are readily recognised by their
pedipalps, which are complex in structure. In addition, the usually
relatively small and slim male abdomen never exhibits an epigyne.
\i{}Mature female\i0{}s have simple pedipalps (though rarely they are
distally expanded), and the relatively large and plump abdomen usually
exhibits an epigyne. \i{}Immature spiders\i0{} inevitably pose problems
for identification. They have modified palps and no epigyne, and are
often pale (sometimes almost translucent) and of relatively fragile
appearance. 
#46. \i{}Epigyne\i0{} (epigynum): a sclerotised plate, borne by most
adult female spiders on the underside of the abdomen in front of the
epigastric fold. It forms part of the reproductive apparatus, and
variation in its complexity is of taxonomic interest.
\par{}\par{}\i{}Mature male spiders\i0{} are readily recognised by their
pedipalps, which are complex in structure. In addition, the usually
relatively small and slim male abdomen never exhibits an epigyne.
\i{}Mature female\i0{}s have simple pedipalps (though rarely they are
distally expanded), and the relatively large and plump abdomen usually
exhibits an epigyne. \i{}Immature spiders\i0{} inevitably pose problems
for identification. They have modified palps and no epigyne, and are
often pale (sometimes almost translucent) and of relatively fragile
appearance. 
 
