The Lactrodectus (Black Widow Spider)
Black Widow Spiders are sometimes referred to as shoe-button spiders or hourglass spiders. They are highly venomous, able to adjust how lethal their venom is based on their prey's size, able to produce enough venom to easily kill animals such as dogs and cats, and possibly even horses. Opposite to most other species, the female Black Widow Spider can grow to be almost twenty times larger in mass then that of the males. During reproduction process, the females are known to kill and eat their mates afterward, hence the title "Black Widow." They are commonly found in many temperate climates and all over the US, except for Alaska.
The System
Spiders have an open cardiovascular system, meaning they don't have veins or real "blood." Instead, they have something called haemolymph, which is pumped through arteries into areas called sinuses that surround their internal organs. its heart can be found in the abdomen, and is shaped like a tube above the intestine. Because of certain proteins in the haemolymph, its blood is tainted a faint blue. The aorta extends from the front, or anterior, of the heart up to the spider's head.