If you live in Kansas this is a unwelcom guess you need to recognize. This is the Brown Recluse or Violin spider. You can see the black line on the main body, looking like a upside down violin resulting in the nicknames fiddleback spider, brown fiddler or violin spider. The spider usually bites only when pressed against the skin, such as when tangled up within clothes, towels, bedding, inside work gloves, etc. The initial brown recluse bite frequently is not felt and may not be immediately painful, yet such a bite can be serious. However, the fangs of the brown recluse are so tiny they are unable to penetrate most fabric, including socks.
The brown recluse bears a potentially deadly hemotoxic venom. Most bites are minor with no necrosis. However, a small number of brown recluse bites do produce severe dermonecrotic lesions (i.e., necrosis); an even smaller number of brown recluse bites produce severe cutaneous (skin) or viscerocutaneous (systemic) symptoms. . In one study of clinically-diagnosed brown recluse bites, the incidence of skin necrosis was 37% and the incidence of systemic illness was 14%.