Savory - Arachnida 1977

66 II. DE ARACHNIDIS
Sometimes the prey was held by one pedipalp while the chelicerae were
being cleaned by the other.
The food particle was torn open by the chelicerae, which were thrust
into the wound, where they sometimes remained stationary and were
sometimes moved about. The flooding of the food with secretion from
the chelicera! glands was clearly seen. The duration of a meal was from
1 to 2 hours and was followed by cleaning of the rostral area. There are
differences between the processes of feeding by different species,
depending in part on the presence or absence of venom in the pedipalpi,
and in part on the size and structure of the chelicerae.
Only a slight familiarity with the ways of false scorpions is sufficient
to impress one with the outstandingly potent nature of their venom.
A victim once bitten seems to be at once immobilized; and one has seen
a spider, swinging on its thread, and coming into momentary contact
with a false scorpion much smaller than itself, die instantaneously
when it was bitten. It is tempting to claim for false scorpions that in
proportion to their size, they are the most venomous of all the
Arachnida.
Two topics complete a review of an arachnid's nourishment. The
first is the related problem of drinking.
There is a common belief that scorpions do not drink, and even a
fable that water kills them, but neither statement is true. There are
several species of scorpion that can live only in damp places, where
drinking water is always available. In this they resemble harvestmen,
which drink frequently and, like false scorpions, soon die if the atmosphere
is too dry. On the other hand, there are scorpions and harvestmen
that live in hot deserts, and the former at least are known to be
able to survive because of a well-developed power of water conservation,
due to a wax layer in the cuticle.
The second point is the comparative indifference of many Arachnida
to fasting. Captive Arachnida do not need to be fed every day, and many
a spider is overfed if given a fly daily. A couple of weeks without food
seems to be of no importance whatever, save perhaps to harvestmen,
which do not appear to be blessed with quite the same indifference. But
this is nothing when compared with the feats of survival that have been
recorded by various observers. Iconopoulous kept a scorpion without
food for 14 months, Jacquet kept one for 368 days. Among spiders,
Berland had a Filistata that did not feed for 26 months and Blackwall
a Theridion whose record was 30 months. Baerg has kept a trap-door
spider for 28 months.
Although this has been known for so long, precise investigation of the
spider's condition during a period of abstinence has but recently been
carried out. Anderson ( 1974) kept a number of spiders of two species,
7. BIONOMICS: GENERAL HABITS 67
Lycosa lenta and Filistata hibernalis, the normal life spans of which species
are ten months and several years respectively. During the experiment
the spiders were weighed and measured every fortnight and their
metabolic rates were determined by measurements of their oxygen
consumption.
Kept without food, the Lycosas survived for an average of 208 days
and the Filistatas for 276 days. Their metabolic rates were reduced by
30 or 40%, wit!1 no apparent decrease in their ordinary capabilities;
and if the starving were stopped they quickly doubled their weight.
The most significant result was that differences in survival time were
inversely proportional to the metabolic rates, an adaptation which
increases the individual's chance of coming through a time of natural
scarcity.
The reproductive habits and activities of Arachnida are no less
characteristic than their methods of protecting and feeding themselves.
In all species the sexes are separate and the ova are fertilized internally,
usually by spermatozoa which have been stored in spermathecae and
which enter the ova at the time of laying. The transference of spermatozoa
from the male to the spermathecae of the female is seldom a simple
process; it is preceded by a series of actions, sometimes prolonged and
complicated, which are customarily, if unfortunately, described as
courtship.
This courtship is best known and is perhaps most diverse among
spiders, in which order it takes a wide variety of forms. The vagabond
species of more primitive families usually show little more than a mutual
touching and stroking, after which the male climbs on the back of the
female and inserts into the epigyne a palpal organ which has been
charged with semen. ~fore elaborate preliminaries are shown by spiders
with better eyesight, like those of the families Lycosidae and Salticidae.
The male indulges in a kind of dance: secondary sexual differences such
as black segments on the legs or coloured patches on the body, are
displayed before the female, who appears to watch them as the dance
proceeds. This kind of courtship is more demonstrative among jumpingspiders
than among wolf spiders, and many descriptions of individual
performances have been written and illustrated.
Web spiders do not dance in this way. The male, who with maturity
has abandoned his web and has thereby sacrificed all chance of another
meal, arrives during his wanderings on the outskirts of a web occupied
by a female of his species. His reaction consists either of drumming
vigorously on the web with his palpi or in tweaking or twitching its
threads in some way which does not stimulate the female to rush out as
to a captured fly. In this way he makes a gradual approach until his
forelegs touch hers.