Savory - Arachnida 1977

68 11. DE ARACHNIDIS
This initial contact is evidently a critical point in the meeting of any
two Arachnida in many circumstances. It seems to act as a stimulus to
the curious behaviour first described among harvestmen as "combats
acharnes" (Simon, 1879). These bloodless battles have also been seen by
Weygoldt ( 1971) as occurring between individuals of Amblypygi and
Uropygi. After the first touch the two animals meet with widely separated
pedipalpi, each one pushing and pulling the other. After a few
seconds all is over, one ofthe two retreats slowly and is disinclined for a
second round. That there is no enmity in these displays is shown by the
fact that if many specimens are together in a cage with no room to
manoeuvre there are no battles and all remain peaceably together.
The courtship behaviour found in other orders is not so colourful, but
it is just as unexpected. It has been seen among scorpions, false scorpions,
Amblypygi and Schizomida, and an unmistakable similarity
runs through the performance in all these groups. There are specific
differences, and no doubt when more species have been observed more
often, these courtships will be recognized as constant and as individualized
as they are among spiders. In a shortened and generalized outline
the course of events is as follows. The male grasps the female with
pedipa1pi or chelicerae, and thus united they walk to and fro, at times
varying the routine by some change of position, until, perhaps after an
hour or more, the male secretes a spermatophore (Fig 23).
7. BIONOMICS: GE~ERAL HABITS 69
of the ova should require such preliminaries and suffer such delay. Any
explanation must take into account the habits of two large orders which
have not yet been mentioned, Solifugae and Opiliones.
Among Opiliones there is no courtship and the sexes unite as soon as
two mature individuals meet. The male possesses a chitinous extrusible
penis (Fig. 24), which passes between the chelicerae of the female as
the two animals face each other, and liberates the spermatozoa in a few
seconds. Solifugae show neither display nor dance; the male "caresses"
the female with his legs and pal pi, as a consequence of which she falls
into a state of catalepsy or trance. 'Vhile she is thus unconscious he
picks up a globule of semen in his chelicerae and presses it into her
genital orifice.
Clearly, among Arachnida, courtship is a many-sided phenomenon,
and any explanation of it must not only cover its diversities but should
(I)
( 11)
FIG. 24. l\Iale organs of two han·estmen: (i) Oligolophus and (ii) Xemastoma.
-
FIG. 23. Spermatophore of scorpion, Opisthothalmus. After Alexander.
This is an object produced in gelatinous form from his genital orifice;
it adheres to the ground and quickly solidifies. On top it carries a drop
of semen. The result of the dance has been to bring the female into such
a position that if she is led forwards the spermatophore will enter her
epigyne. This the male does, guiding her accurately, and among false
scorpions then shaking her so that the spermatozoa are detached from
the top of the spermatophore and liberated inside her body.
Both the dances of spiders and the promenades of scorpions are
surprising actions. Clearly instinctive in nature, they ask for an explanation
of a kind that will help us to understand why the vital fertilization
also be applicable to other classes of invertebrates, such as insects and
molluscs, which exhibit parallel forms of action. An attempt to do this
is included in Part V.
Behaviour that may be described as peculiar to motherhood is found
sporadically among Arachnida. ~Iany leave their egg-cocoons to their
fate, and are themselves dead before their young are hatched. The
exceptions are chiefly to be found among the spiders that carry their
cocoons about, either in their chelicerae or clasped under the sternum
by pedipalpi and legs or attached by a short silk thread to the spinnerets.
The last of these, shown by all wolf spiders of the family Lycosidae is the
most familiar, and is a habit shared by only a few others.
Among the Lycosidae the cares of motherhood are extended to the
carrying of her young on her back for a time after they have left the
cocoon. The habit has been investigated by Rovner et al. ( 1973), who,