Araneidae: Orchard Orb weaver (Leucauge venusta); Christine, The Woodlands, Texas--08.11.07

Orchard Orbweaver (Leucauge venusta), Christine, The Woodlands, TX; 08.11.07--Ventral Body, Center of Web

Christine wrote:

“Hi—Me again. Here are the other two photos.”

[Editor's Note: I had received a series of emails from a woman named Abigail, in Houston, in the previous week, describing without benefit of photography what I supposed to be an orchard orbweaver, so I wondered if Christine was Abigail, now writing under a nickname. She turned out to be a different person, however, whose first message had not yet arrived. The Woodlands, Texas, is located north of Houston, on Interstate 45].

As Willis John Gertsch pointed out on pg. 172 of his 1979 book, American Spiders, “The species of Leucauge are brilliantly colored spiders, green and silvery white, often spotted with gold, orange, or copper; and our commonest species, venusta, well merits its name of beautiful.”  It is a tiny spider, though, and one we are apt to miss unless we are very observant as we tarry in wood and glen to watch the myriad of organisms that scurry about, or–in the case of the Orchard Orbweaver–sit and wait for food to arrive at her web.

Notice that the frame threads of this Leucauge venusta web, at its edges, are outside the range of Christine’s photograph, but the hub, attachment zone, and radial threads, along with many spiraling catching threads, are visible. This simple symmetrical orb is characteristic of many orbweavers, including Argiope aurantia and Gasteracantha cancriformis, but varies from the slightly eccentric orb of Nephila clavipes, whose hub is constructed nearer the top than the web’s lower region. The open hub is distinct from the closed hub of Argiope aurantia, but is similar to to the open hub of Nephila clavipes.

There appear to be 33 radial threads, and at least as many spiral catching threads, with five or six spirals in the attachment zone that borders the open hub. As with Nephila clavipes, the clot of threads in the upper portion of the open hub is presumed functional, though the exact function is in dispute. Likewise, the confusion of threads halfway down the two radial threads between the spider’s first legs, also has a purpose, probably associated with prey catching. Radial threads are rigid, and serve as communicators to tell the spider not only that prey has impinged upon the orb, but also to vector attention to the prey’s location.

Orchard Orbweaver (Leucauge venusta), Christine, The Woodlands, TX; 08.11.07--Dorsoposterolateral body

The dorsal coloration of this spider’s carapace is yellowish, or orange-green, with dark stripes on the sides. The abdomen is bulbous at its dorsal anterior aspect, and narrows somewhat posteriorly, with a silver-white background on which are impressed dark green lines laterally, with a narrow median black stripe that broadens, then separates into three stripes enclosing whitish blotches medially, and flanked by orange blotches at the lateral posterior abdomen. The femoral and tibial segments of each leg are green, while portions of certain patella-femoral joints have an orange cast.

The female Leucauge venusta ranges in size from 5.5-7.5 mm (0.22-0.30 inch) in length. Keep that in mind when viewing these photographs, as this is a miniscule animal with a body rarely more than a quarter of an inch long. The crouched legs stretch forward another half an inch, and backward a quarter of an inch more, making the entire mature spider about an inch long.

Ventrally, this spider has a bright green background coloration on which two yellowish spots flank the spinnerets, and two comma-shaped orange markings, nearly joined at their anterior extremities, dominate the middle of the ventral abdomen. The book lungs, anterior to these but separated from them by narrow yellowish strips, appear covered by a yellowish plate, with darkened respiratory slits at their posterior margins. The book lungs are separated by an epigynum whose architecture cannot be discerned in the present photograph.

Orchard Orbweaver (Leucauge venusta), Christine, The Woodlands, TX; 08.11.07--Ventral body closeup

*Note: The common name of this spider, the orchard orbweaver, is listed in the authoritative “Common Names of Arachnids, Fifth Ed., 2003″, published by the American Arachnological Society Committee on Common Names of Arachnids. Only two species of Leucauge are found in the United States. Besides Leucauge venusta the literature mentions Leucauge argyra, but I have not yet found definitive, discriptive material on the latter.

jc