Eyes can be arranged
differently in different species. Sometimes one pair is better
developed than the rest. Some species have a pair less or are
even without eyes. While several families of hunting spiders have
good to excellent vision (Lycosidae and Salticidae), the members
of most families of hunting spiders, most of the web weavers,
and the spiders that lurk on flowers and other fixed locations
waiting for some insect to come their way have very poor eyesight.
Instead, these spiders hunt using their extreme sensitivity to
spiders have no antennae (feelers). Instead, they have pedipalps,
sometimes just called palps, which are two additional appendages
next to their mouth parts that, besides having other functions,
they use to help themselves manipulate the food that they eat.
Spider haemolymph (the equivalent of blood) does not circulate
through vessels, but just fills the body of the spider. This is
called an open circulatory system. The spider's respiratory anatomy
is based on a tracheal system, with each opening to the trachea
as an extension of an outer pore reaching from the spider abdomen,
protected by spiracles which are pores in the spider exoskeleton,
composed of chitin.
Image Number 1 Comes From The N.R.C.S.
Images 2 Through 5 Comes From The U.S.F.W.S.
Images 6 Through 8 Come From N.O.A.A.