Author: Jim Carrel
In the past three years information about every spider species archived in the museum collection at the Archbold Biological Station has been computerized. Each listing for 482 preserved individuals includes the spider’s scientific name (taxonomic family, genus, and species), latitude and longitude for where it was collected, as well as the month and year it was found. This information recently became available free-of-charge to anyone in the world at the web site Global Biodiversity Information Facility (www.gbif.org).
In September Dr. Jim Carrel, Research Associate at Archbold and former professor at the University of Missouri, eagerly looked at the new spider data set and found some interesting outcomes. Carrel reported, “The entire collection contains 20 families and 116 species of spiders, which likely is less than half of the various kinds that dwell in Highlands and Polk Counties. Hence, there’s much more field work to be done to get a reasonable inventory of the spiders around us.” He estimates, based on spider surveys he and others have done in northern states, that there may be somewhere on the order of 700-1,000 spider species in all of Florida.
Carrel also found that the kinds of spiders in the Archbold collection represent what appears to be a highly nonrandom assortment relative to all the common species known to occur in North America. Specifically, there were three to five times as many jumping spiders, family Salticidae, and orb-web spiders, family Araneidae, than one might reasonably expect if quantitative sampling had been conducted. When he plotted these data, Carrel immediately sensed why this discrepancy had occurred. He said, “Going back decades to the time when Mr. Archbold was alive, spider experts (arachnologists) from Harvard University, Cornell University, the University of Florida, and other institutions who specialized in research on these two families came often to Archbold and made extensive collections of these showy spiders. They kindly deposited some of their trapped spider specimens here in Archbold’s permanent collection as reference material for future researchers.”
Carrel found that the Archbold spider collection also was grossly underrepresented with sheetweb spiders, family Linyphiidae, and meshweb-weavers, family Dictynidae. He fully expected this outcome. Carrel explained, “These spiders generally are tiny, mostly pinhead size. They hide near the ground and in curled leaves. And there are lots of hard-to-tell-apart species. Few experts in the world can identify them. By comparison, jumping spiders and orb-weaving spiders are much more attractive because they are big and easily detected up on plants.”
Field studies conducted in the past three decades at Archbold have revealed valuable information about the natural history of local spiders. Extensive collections in native and disturbed habitats up and down the Lake Wales Ridge by Dr. Mark Deyrup, Emeritus Research Biologist at Archbold, and Carrel demonstrated that nine spider species are restricted largely to the pristine Florida scrub ecosystem. Long-term projects have provided clues as to why some of these spiders are ‘scrub specialists’. For example, Carrel and Deyrup found that the exceedingly rare Red Widow Spider feeds primarily on types of dung beetles that live only in scrub. Carrel explains, “These beetles are bulky and fly low through gaps between the palmettos and shrubs. The widow spiders deliberately build their tangle webs across gaps and trap unsuspecting beetles.” Carrel also found that Red Widows have a strong preference for native scrub that had been burned 1-10 years ago. “Scrub habitats naturally experienced frequent fires in prehistoric times and all of the palmettos and other perennial plants survive and quickly resprout after a burn. If fire is excluded,” he goes on to explain, “then the scrubby vegetation gets taller than a person and the gaps disappear, making it unsuitable for Red Widows.”
Five wolf spiders, all in the family Lycosidae, also are scrub specialists. Archbold researchers showed they survived and thrived after the habitats were burned. Spiders managed to survive a fast-moving blaze by hunkering down in their burrows, insulated from the flames and heat by several inches of cool sand overhead, much as is done by Gopher Tortoises and Florida Mice. After fires, wolf spider populations increase because there were more open gaps of barren sand suitable for burrowing and insect prey also might have been easier to catch since there was little leaf litter to hide in. While doing time-consuming burn studies with spiders in the wild, Carrel had plenty of time to ponder related questions, such as “How did Native Americans and early settlers cope with landscape level wildfires that often raged in May or June before onset of the wet season? If they weren’t near a lake or stream, did they scamper for open sandy spots, such as Rosemary balds, and make a ‘fox hole’ as a last-ditch attempt to survive? What would I do if put in their shoes?”
In contrast web-spiders, for the most part, do not survive burns in native Florida habitats. They use an alternative strategy: shortly after hatching from eggs, they recolonize by drifting aimlessly for long distances in the breeze on long silken threads, called ballooning. It is almost certain that the Red Widow spiders do this, but nobody has documented it. Fall and spring are prime seasons for spider ballooning activity. Thus, when Halloween rolls around at the end of October, remember that trick-or-treaters will be joining all the spiders out and about in the evening as the sun sets over Central Florida.