Black widow spiders are among the most recognized arachnids, often identified by a distinctive red marking on their underside. This iconic symbol is widely associated with them, leading many to wonder if every black widow displays this particular red marking.
The Iconic Red Marking: Is It Always There?
The classic red hourglass marking is most typically found on the underside of the abdomen of mature female black widow spiders, such as the Southern black widow (Latrodectus mactans) and Western black widow (Latrodectus hesperus). This marking usually appears as two connected red triangles, forming the hourglass shape. Females often hang upside down in their webs, making this ventral marking clearly visible.
Not all adult female black widows possess a perfectly formed red hourglass; some may have two separate red spots or, rarely, no prominent red marking. The exact shade or shape of the hourglass can also vary. Male black widow spiders are considerably smaller than females, often gray or brown rather than shiny black. Males frequently lack the prominent red hourglass, instead displaying red and white stripes or spots on their abdomen, or sometimes yellow or white hourglass markings.
Juvenile black widows also present a different appearance. Young spiders often have markings that include orange, brown, and white, or a grayish-black body with white stripes and yellow or orange spots. These distinct patterns gradually darken with each molt as the spider matures. The red marking common on adult females is typically absent or appears differently in these younger stages.
Beyond the Red: Other Identification Clues
Since the red hourglass is not a universal identifier, other physical and behavioral characteristics can help identify black widows. Mature female black widows generally have a glossy black, bulbous abdomen. Their legs are long and slender in proportion to their body.
Black widow spiders construct irregular, tangled, three-dimensional webs. These webs are notably strong and sticky, designed to ensnare prey. They are typically built in dark, undisturbed locations close to the ground, such as under ledges, in woodpiles, sheds, garages, and basements. Black widows are typically shy and solitary, primarily active at night. They prefer to avoid confrontation and will often attempt to flee when disturbed, only biting defensively if threatened or guarding an egg sac.
Diversity Among Black Widow Species
The term “black widow” refers to several species within the Latrodectus genus, which encompasses approximately 30 species found across the globe. In North America, common species include the Southern black widow (Latrodectus mactans), Western black widow (Latrodectus hesperus), Northern black widow (Latrodectus variolus), Red widow (Latrodectus bishopi), and Brown widow (Latrodectus geometricus). These species exhibit differences in their markings, highlighting that the red hourglass is not uniform across the group.
For instance, the Northern black widow often displays a broken or split hourglass marking on its underside, and may also have red spots or stripes along the top of its abdomen. The Red widow is characterized by a reddish-orange body and legs, with a black abdomen that typically features red or orange spots outlined in white or yellow on its dorsal side, often lacking a complete hourglass. The Brown widow is usually tan or brown and has a less distinct, duller reddish hourglass marking. Some species may even have hourglass markings that are orange or yellow.