BRITISH HARVEST-SPIDERS 183
hand or toe segment, when the long limbs are one of the con-
spicuous features of most harvest-spiders?
Both scientific and popular names indicate the association of
harvest-spiders with fields, and Dr. Bristowe (ibid.) reminds us
of the old Essex superstition that it was unlucky purposely to
kill a harvest-spider because of the belief that these creatures
helped farmers with the scythe, rake and sickle which they were
alleged to possess !
Harvest-spiders are almost world-wide in their distribution.
They flourish particularly in humid tropical regions, but become
scarce as the arctic and antarctic regions are approached. They
are divided into three sub-orders only one of which is represented
in this country. Our twenty-one species are not difficult to
identify and most can be recognised at sight after a little practice.
The young stages are more difficult to determine.
The world monograph on this group has been written by Dr.
Roewer (1923) and the British species can be determined by Dr.
Todd's key (1948). In the latter work the author has raised
Opilio saxatilis (C. L. Koch) to specific rank basing her con-
clusions on external characters. I have since confirmed this
work (Sankey, 1949). Two other useful works on harvest-spiders
are those of Simon (1879) and Hansen and Sorensen (1904).
BIONOMICS
The legs : in contrast to true spiders no regeneration of the
limbs occurs in harvest-spiders. A minimum of four legs, pro-
vided one of the second pair remains, enables those specimens
which I have studied to lead a more or less normal life. The legs
can be autotomised, but if both of the second pair are lost death
soon follows.
The second legs seem to be used for tactile purposes and
possibly for smell perception, and the sensory hairs on the first
legs may also serve the latter purpose. It is of interest to note
that the family with the longest legs (Phalangiidae) possess two
small spiracles (breathing holes) on the tibia (fifth segment) of
each leg in addition to the two usual spiracles which open near the
basal (coxal) joint of the fourth pair of legs. From these spiracles
the breathing tubes (tracheae) ramify to all parts of the body and
respiration takes place in the same way as in insects. There are a
number of other structures on the legs and on palps whose func-
tions are uncertain.
To the lyriform organs, which are button-hole shaped slits
found singly or together in a lyre-shaped group, have been
attributed the function of smell. These occur especially on the
first segment of the chelicerae and on the coxae of the legs. Each
is supplied with a nerve ending. McIndoo (1911) after getting