Biologist Discovers That Red Widow Spiders Eat Scarab Beetles

Posted on March 20, 2014

University of Missouri biologist James Carrel discovered that Florida's elusive red widow spider likes to eat scarab beetles. The red widow spider is venomous, but no bites from the spider have been recorded. Carrel's study found that the red widow primarily preys upon species of scarab beetles common to its Florida scrub habitat.

Carrell, Curators Professor Emeritus in the MU Division of Biological Sciences, says in a statement, "The pine scrub habitat, found on sandy ridges in Central and Southeastern Florida, is one of the oldest in North America. Many of the plants and animals found on these ridges, including the red widow spider, are restricted to these high, dry areas. Our research suggests that red widows have evolved to specialize on scarab beetles because they are reliable food sources."

Red widow spiders conceal their funnel-shaped retreats in unopened palmetto leaves, which makes them very difficult to spot. The spiders' presence is only visible on foggy mornings during four months of the year. This is when threads spun loosely between tips of palmetto fronds can be spotted. Carrel has been monitoring populations of red widows at the Archbold Biological Station since 1987. Only twice in 23 years - in March 1989 and in May 2003 - were enough webs located so that the dietary habits of the spider could be studied. Pictured below is Trigonopeltastes floridana, a scarab beetle endemic to the Florida scrub that the red widow spider preys on.

Carrel's study, entitled "Red widow spiders prey extensively on scarab beetles endemic in Florida scrub," appears in the March issue of Florida Entomologist.

SPIDERS