Known as spiny orb-weavers, there are 119 species in the Micrathena genus, of which only 4 are found in the United States – the spined micrathena, arrow-shaped micrathena, and white micrathena. All are common in woodland areas in the eastern portion of the country (the fourth, Micrathena funebris, is found only in the southern US so I am unable to include it here). Diurnal orb-weavers, micrathenas can be found sitting in their webs in the daytime. The females of these species have distinctive abdomens with varying amounts of spiky tubercles. Possible explanations for the spines include defense – they make the spiders look much less appealing as prey, and camouflage – a jagged body shape blends in with its surroundings better than a smooth, circular one. All species are completely harmless to humans. The descriptions of these three species refer only to females. Males are typically half the size of the females and less ornate in appearance, lacking large spines and bold coloration.
Micrathena gracilis, the spined micrathena, has a large abdomen that is black and white/yellow with five pairs of spines. Viewed from the side, the abdomen is somewhat triangular. The largest of these three species, females are up to 10mm in length.
One of the challenges of shooting these spiders is depth of field. Their abdomens and all the spines are difficult to capture in complete focus at macro magnifications. The first photo above of the spider eating a fly is a focus stack of four images, which was necessary to make the entire abdomen appear sharp. The view is from below the web, looking up – the spider sort of sticks out perpendicular to the web. The spider in the second photo was actively working on its web, meaning focus stacking was not an option so I shot at f/11. I usually like to shoot at f/5.6, which is the sharpest aperture setting on my Laowa 60mm, but when I need a little more depth of field in a single frame I’ll go down to f/11. I don’t use f/16 or f/22 since there’s too much diffraction softening for my liking.
Micrathena sagittata, the arrow-shaped micrathena, is unmistakable with its yellow abdomen and large black and red spines. Females are 8-9mm in length. The etymology of the name sagittata may be familiar to some – “Sagittarius” is Latin for “archer.”
This photo is a focus stack consisting of eight images. Fortunately, this individual stayed still just long enough to get those shots. The second photo is a crop to show the beautiful color and texture of the abdomen.
Micrathena mitrata, the white micrathena, is the smallest of these three species with the females being approximately 5mm in length. Due to their size, they can be easy to overlook but they are no less striking than their larger relatives. The females have short spines on the end of their abdomen, which is mostly white with black and red markings.
The white micrathenas I have encountered have been a little trickier as photographic subjects because of their small size. Like many other spiders, once they’re aware of your presence they have a tendency to just abandon ship and repeatedly drop while tethered to a silk line. With some patience, however, photos can be made when they climb back up their line and rest for a moment. The second photo is a stack of two images, one focused on the head and one on the abdomen.
Andrew Murray Photo 