After a few months of serious work during which I completed my PhD dissertation defense, I finally have time to blog about spiders again. My friend Andrew Durso recently went to Florida to help collect lizards in a very interesting field study to investigate the evolution of populations on different islands. While Andrew is an accomplished herpetologist, he is interested in natural history in general, and was able to take some spider pictures on a small island in the Matanzas River estuary. This estuary supports a diversity of native habitats and wildlife of national importance.
The spiny-backed orbweaver (Gasteracantha cancriformis) is a pretty spider typically found in woodland edges in the southern United States down into South America. This web-building species, which has six conspicuous abdominal spines, shows interesting geographical variations in color and shape. For instance, the individual photographed by Andrew had a white abdomen and red spines, but individuals that I have seen in Colombia had a yellow abdomen with black spines. It has been suggested that conspicuous colors in spiders may increase their foraging success via the attraction of prey to these colors, but a recent study suggests that this is not the case in Gasteracantha.
White and red Gasteracantha cancriformis, Florida
Yellow and black Gasteracantha cancriformis, Colombia
Andrew also noticed a few Phidippus jumping spiders, which have typical metallic blue-green chelicerae. These individuals appear to be P. regius (the regal jumping spider), which is the largest species of jumping spider in the eastern United States, and relatively common in Florida. Males are black with white markings on the abdomen whereas females can be grey or orange. The male P. regius can be distinguished from the somewhat similar-looking male P. audax by the shape of the posterior abdominal spots, which are oval in P. regius and more linear in P. audax.
Female P. regius
Male Phidippus, likely P. regius
P. regius is usually found in open habitats such as fields or open woods. Females lay their eggs in thick silken nests under the bark of trees, but cracks and spaces in houses may also provide suitable shelter.
Hello. I am wondering if you can help me understand what kind of spiders that are living in my Live Oak trees. We live in Apopka, FL which is north/north west of downtown Orlando, and it is very country living in this area. Last evening we were taking care of other issues (a squirrel who has taken up residency in our attic) and we were walking in our backyard at dusk… when all of a sudden and very rapidly these rather large (in my opinion anyway) spiders made a decent out of the trees. There were four of these all about the same size coming from different trees at the time. I am certain there are many more, but that is all we could see with the light going away and nightfall coming on quickly. When threatened with a spray bottle of water, these spiders went back up the single strand of web material with great speed. Originally they were curled up with their legs and I thought it to be a leaf dangling on a web/thread. But I was pretty freaked when I saw their capabilities and wondered what kind of spider they are and if they are poisonous. We just moved here from out of state and we did not have spiders like this in our past. Unfortunately I could not determine any colors or patterns in the dark… the only thing I could see is when they extended their legs to double their size and that I saw something white under them and thought this to be an egg sac. Can you help? I know this information provided is vague, but thought perhaps by the characteristics of living in trees, sliding down a single strand and rapid movements along with size could be enough for a start. Thank you. Bill Morelli August 12, 2012
Hi Bill, thanks for your spider story! Florida has some really neat spiders because of its tropical/subtropical climate, which allows species from more southern latitudes to thrive. Did you notice if your spiders came from a web? The use of a single strand of silk is very common in spiders, which use it as a safety line that keeps them attached to the substrate. Web spiders typically use a safety line, but even jumping spiders, which do not rely on webs to hunt, use a safety line as they walk around. As a result, the use of a safety strand of silk is not really a diagnostic characteristic. The rapid movements you observed are also pretty typical of spiders that feel threatened. Is there any chance you can take pictures when you see these spiders again? If you manage to take pictures, feel free to send me a couple. Some conspicuous and relatively common web-building spiders in Florida include Nephila (golden silk orbweaver), Argiope (garden orbweaver), and Gasteracantha (spiny-backed orbweaver). As far as I know, the spiders you should be concerned about in FL are mainly the black widows and the brown recluse, but these do not fit with the habitat you described (trees). The spiders you observed are most likely harmless… I hope this helps a little!