Spider identification

Caveats for identifying spiders

The information presented in the matrix key is based on having a complete and intact specimen. However, spiders are fragile and may be easily damaged during shipment or during destructive collection, and may be missing certain diagnostic features. Also, some of the scales and body hairs, particularly on the legs and carapace, can rub off fairly easily, so you may need to take this into account.

Occasionally, reproductive structures may not be in pristine condition. Some males break off portions of their palp inside the female to prevent subsequent males displacing their sperm. Therefore, critical male structures may not appear as perfect as in the provided images. Additionally, the female genital opening may appear to be an amorphous blob. This may be a mating plug placed by the male to prevent subsequent males from mating, or it could be solidified leakage of female bodily fluids. These can be peeled off so you can see the female structures. Neither of these events happen often, however, you should be aware of the possibility for this to occur.

The cardiac region is on the anterior dorsal surface of the abdomen and is longitudinal in shape. In most spiders, the pigmentation of the skin covers this region. However, in spiders with pale integument, most notably Cheiracanthium and Trachelas spiders, the skin is so thin and pale that the cardiac region may appear to be a different shade than the rest of the abdomen. You might even be able to see the heart pumping in live specimens. For the purposes of this key, because this apparent coloration difference is not due to a pigment, the abdomen should be considered monochromatic.