The brown recluse spider (Loxosceles reclusa) is one of only two spiders in North America with medically significant venom. Public concern often leads to questions about its presence in regions like New Hampshire, where many harmless, brown-colored spiders reside. This article addresses the definitive range of the brown recluse and provides the information necessary to accurately distinguish it from the spiders native to New Hampshire.
The Confirmed Native Range of the Brown Recluse
The definitive answer to the question of the brown recluse’s presence in New Hampshire is that it is not a native or established species in the state. The spider’s natural, established range is primarily confined to the South-Central and Midwestern United States, extending from southeastern Nebraska to southwestern Ohio, and south through Texas to northern Georgia. New England’s climate, characterized by colder temperatures and different humidity levels, is largely inhospitable to the establishment of a breeding population outside of human-controlled environments.
While a brown recluse might occasionally be found in New Hampshire, these are isolated incidents of “hitchhikers.” Spiders can be inadvertently transported from their native range via moving boxes, freight, or long-distance travel, arriving as transient individuals. These isolated spiders do not constitute an established population and do not indicate that the species is breeding or spreading within the region. Reports of brown recluse bites outside this established zone are often attributed to misdiagnosis of other medical conditions, such as bacterial infections.
Key Features for Identifying the Brown Recluse
Accurate identification of the brown recluse relies on a combination of specific morphological features, not just a single marking. The most famous characteristic is the dark, violin-shaped marking located on the spider’s cephalothorax, with the “neck” of the violin pointing toward the abdomen. However, this marking can be indistinct on some individuals, and other harmless spiders may exhibit similar patterns, making it an unreliable sole identifier.
The most reliable feature for identification is the spider’s unique eye arrangement. While most spiders have eight eyes arranged in two rows, the brown recluse has only six eyes, configured in three pairs (dyads) in a semicircular pattern. The recluse’s legs lack the thick, conspicuous spines found on many other spiders, having only fine, short hairs instead. Their body is generally a uniform color, ranging from light to medium brown, and they are relatively small, typically between 6 and 20 millimeters in body length.
Common New Hampshire Spiders That Are Misidentified
The confusion surrounding the brown recluse in New Hampshire stems from the presence of several common, brown-colored spiders that share a superficial resemblance. The Woodlouse Hunter spider (Dysdera crocata) is frequently mistaken for a recluse, particularly because it is also a reddish-brown color and prefers secluded, dark, damp areas. This spider is easily distinguished, however, by its massive, prominent chelicerae (jaws) and its distinctly colored abdomen and cephalothorax, which are not a uniform brown.
Another common look-alike is the Wolf Spider (family Lycosidae), a large, hairy, brown hunting spider often seen running across floors. Wolf spiders are significantly larger and have eight eyes arranged in three rows, including two very prominent posterior eyes, immediately ruling out a brown recluse identification. The American House Spider or certain Cellar Spiders, which are also light brown, can be identified by their eight eyes and the messy, disorganized webs they rely on. These local spiders, while potentially alarming due to their size or speed, pose little medical threat to humans.