Arachnid life and [not] death

Click for greater clarity.

During my reconnoitering through Great Hills Park on May 2, about half an hour before I encountered the green anole that graciously put on a display for me, I noticed a funnel web in the low vegetation next to the trail. Not knowing if a spider was waiting inside the funnel to pounce on any small prey that ventured onto the outer portion of the web, I knelt to have a look. When I did, I could see that there was indeed a spider in the narrow part of the funnel, but then to my surprise I noticed that there was also a dead spider at the top of the outer part of the web.

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Update: In a comment below, Spider Joe explained that what I took to be a dead spider was actually the cast-off exoskeleton of the live spider in the funnel. See his detailed comment for more information.

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For the technically minded, I’ll add that this forested part of the trail was pretty dark, so I turned on my flash and stopped my macro lens down to a small aperture for extra depth of field.

© 2012 Steven Schwartzman

Visitors to Tetraneuris scaposa

The other day you saw Tetraneuris linearifolia, one of two very similar species that share the vernacular name four-nerve daisy. Today’s picture shows the other species, Tetraneuris scaposa, and it shows that I was hardly the only one visiting it on the afternoon of February 15 in northwest Austin. If you’ve been checking this blog for a while, you’ve often heard me talk about how I sit and lie on the ground: those low vantage points reveal a lot that would go unnoticed if I were standing up and looking down at my subjects. In particular, a lot of insects hang out underneath flowers, and so do the spiders that stalk them. I’m assuming that the green insects are aphids; in addition to the two larger ones, there are several smaller ones that are harder to see. As for the spider, notice the net-like patterning on its abdomen and how long its legs are. After looking at several sources, I’m thinking that this is a spider in the genus Tetragnatha, but if anyone can be more precise, please let us know. (Update on Feb. 28: Spider Joe Lapp says that this is likely to be Tetragnatha laboriosa; from a different picture I sent him of the spider he was able to tell that it’s a male.)

As for the four-nerve daisy, if you look at the rays in the 1 o’clock and 5 o’clock positions, you can count the four “nerves” that give these flowers their common name. I don’t know what caused the reddish area on the ray at the upper right. I do know that the downiness covering the stalk and the receptacle of the flower head is a prominent characteristic of both of these Tetraneuris species (and we recently saw a similar fuzz on silverpuff, their not-so-close sunflower family relative). For more information, and to see a state-clickable map of the places where Tetraneuris scaposa grows, you can visit the USDA website.

On the technical side, it may look like I used flash for this picture, but I didn’t. Yellow is a difficult color to photograph in bright sunlight, which was the case here, and in exposing for the intense brightness of the yellow rays I ended up with a background that is close to black. For that and other photographic considerations, you can see points 1, 3, 4, 10, and 18 in About My Techniques.

© 2012 Steven Schwartzman

The not-dried-out on the dried-out

The last two posts showed the predilection of the mustang grape vine to twist, whether it’s young or old. Even when the vine’s tightly curled tendrils dry out, they often last for a long time; with only faint vestiges of red* from the time when this tendril was young, its later and longer-lasting color scheme made for harmonious camouflage.

For more information about Vitis mustangensis, and to see a state-clickable map of the places where it grows, you can visit the USDA website. To find spiders in nature, look almost anywhere.

UPDATE: In a comment on February 27, 2012, Spider Joe Lapp added this information: “That’s a Pirate Spider (Mimetidae), genus Mimetus. They eat whatever they find in other spiders’ webs, including caught bugs, egg sacs, and the host spider.”

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* I’m reminded of the stele (upright monuments) at the great Maya city of Copán. The ancient Maya carved them from stone, but then they painted them, and to this day traces of the original painted colors remain on some of the stele after more than a thousand years.

© 2012 Steven Schwartzman

Aftermath of a drama

A green lynx spider with a bee; click for greater detail.

The last four posts have featured photographs showing stages in the development of jimsonweed, Datura wrightii. Just minutes into the October 24 photo session that led to those pictures (and many more), I came across the aftermath of a little drama* that had taken place on one of the jimsonweed flowers. I’d noticed that quite a few bees were attracted to those blossoms, and apparently a green lynx spider, Peucetia viridans, had noticed that attraction too and had lain in wait; here you see the result of that watchful waiting. As a bonus, though maybe an anticlimactic one, you get to see more details of a jimsonweed flower: its pistil and some of its flattened stamens that are curiously reminiscent of the bee’s wings that are temporarily near them.

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* This is the second little drama of this type I’ve presented so far, the first being on August 23 in a different color scheme, with the victim still struggling, but ultimately with the same fatal outcome as shown here.

© 2011 Steven Schwartzman

Camphorweed Chaos

Seeds caught on drying flowers of camphorweed, Heterotheca subaxillaris; click for more detail.

Yesterday’s post showed a fully open flower head of camphorweed, Heterotheca subaxillaris, on the prairie site of Austin’s former Mueller Airport. Call that the idealized camphorweed picture.

Within a few feet of that bright and well-behaved day’s eye—daisy to us now—was the miniature landscape you see today. This is more typical of what’s out there in nature: chaos. Failure mixes with success. The two flower heads in the center are drying out—notice their tightly curling rays—perhaps without ever turning into the tan puffballs that are normally their next incarnation. Chalk it up to the drought, and no one will argue with you. As is true for most plants, this one has spiderwebs on it, spiderwebs that collect debris, dust, stray objects blown by the wind. Now add the stickiness of camphorweed itself. Result: parachuted seeds trapped in places where they do no good. Do you see five of them? Let’s count:

•  the long, dark seed at the bottom, a bit left of center;
•  the one resting on its side on the rim of the narrower flower head;
•  the one stuck to the bulging base of that flower head;
•  the one at the top of the picture, a bit left of center;
•  the one stuck to a stem in the upper right.

Will any of these seeds ever make it into the prairie soil and begin to grow? If not these, then others, because dozens of camphorweed plants had sprung up around the place where I sat. But all, they and any descendants whose seeds don’t blow far enough away, are still doomed, for this part of the old airport is scheduled to be built on.

© 2011 Steven Schwartzman

Predation on the rays of a sunflower

Although lady beetles eat aphids and other insects, I’ve seldom seen them do so. In contrast, I often come across the remains of spiders’ meals in their webs, and sometimes I find their prey still live in their grasp. I witnessed one such encounter on an early sunflower a month ago in the prairie restoration at Austin’s old Mueller Airport. You can get an idea of the scale of the little drama shown in the photograph from the fact that the body of the crab spider, which Spider Joe Lapp has identified in a comment below as Mecaphesa dubia, was less than half an inch long from fore to aft. I watched for a good while as the tiny caterpillar continued to writhe in a vain attempt to break loose from the spider’s firm grip, a grip that never faltered even as the spider dragged the caterpillar around on the sunflower from time to time in response to my close presence and movements as I kept taking pictures.

Update on August 23, 2011: Valerie Bugh has identified the tiny (and doomed) caterpillar as belonging to the flower moth genus Schinia.

© 2011 Steven Schwartzman