Sunday, October 25, 2015

Fall trip to Tucson.

We left the house on the last day of September and drove out to Arizona to visit my son Gawain and his girlfriend Heather in Tucson. The monsoon was lingering late this year and there was tall grass growing along the roadsides as we entered the state, and the mountainsides were unexpectedly green. The sky was often cloudy for our stay, and we had occasional very heavy rains. The temperatures were comfortable, 80s by day (instead of 100), 60s at night. Afternoons and evenings and weekends we spent together, but during the day when they were busy with their work Cheryl and I were left on our own.

This was no hardship in Tucson and we spent beautiful days at our favorite places. For instance, the water conditioning plant with its acres of rich wetlands ringed with trails. This is a place mostly for birding (best, the day we went, was a handsome prairie falcon chasing killdeer around the waste ponds). Another day we went to Saguaro West with its many trails (we like walking up the dry washes), and we visited local botanical gardens, but over and over again we visited our favorite, Saguaro East, a thorn-forest wilderness that looks like a planted garden of desert plants and trees, each trail or dry wash passing through a different habitat.

It was a different time of year from our past visits so we were interested in what creatures we might see. Herps were interesting. Desert Spiny lizards we had seen before (they're fairly common) but this time they were more in the open and we saw them better. The particularly handsome local race is called Purple-backed Spiny Lizard. I like the way the yellow scales and blue scales meld into green scales down on the tail.

Because it had rained and there were some new surface puddles, the Red-spotted Spadefoot Toads were out. This was the first time we had timed it right to see them. In our walks we had caught glimpses of them disappearing down holes, but it wasn't until we visited our friends the Braddys on the edge of Tucson that we rescued one from their pool and so got to see it up close.

These little guys show one of the extreme measures amphibians can take to survive in the desert. A hard sharpened area on the inner edge of the inner toe on each leg (you can see the yellowish bump clearly at the base of the inside toes in the above picture) allows them to dig into the soil, where they remain for most of the year. When it rains, they are ready. They come hopping out and look for anything moving to put in their stomachs (this being their only chance to feed), meanwhile singing nonstop all night (this being their only chance to breed), then as quick as they can, they lay their eggs in every temporary pond, hoping their offspring can get through the tadpole-to-adult stage before the pond evaporates (in warm weather the whole process from egg hatch to metamorphosis takes as little as two weeks). Then everybody digs down into the soil to wait months for the next rain.

We also saw a couple of very nice small mammals. If you have walked through  the desert, you have seen packrat nests, a meter-diameter pile of old dried cactus fronds, other detritus, sticks and stones, anything else around that a small rodent could drag into the mix. The nests are obvious everywhere, but seeing the packrat that lives underneath (more correctly, the White-throated Wood Rat), is trickier. You aren't supposed to feed the wildlife, but we were eating our lunch, and before we knew it we had dropped a few large juicy grapes on the ground near a nest, which was enough to lure out the occupant. He was quite endearing, despite being, well, pretty ratty.

But the next animal we saw was the star of the trip. We walked around a corner of the trail, and a big animal went bounding off. Through the brush I saw a flashing white rump and huge ears.

"A deer!" I shouted at Cheryl, but I was already changing my mind. "Or was it a huge jackrabbit?"

Cheryl was a few paces ahead of me, and she saw it where it had come to a stop around the other side of a big bush.

"A jackrabbit," she said.

But it was quite unbelievable, an enormous woolly animal with a highly intelligent face, more like something from Alice in Wonderland or some other child's fiction. It was watching us with great interest. "I'm late," it might have said.

We had to wait for it to wander off before it would stick up its marvelous ears, and we could get a picture of them.

We looked him up: this was the Antelope Jackrabbit, the largest and heaviest of his kind. His name comes from the huge white antelope-like rump that he could flash when he was running away, probably to alert other rabbits in the vicinity that there was a predator approaching.

However this is meant to be a blog about invertebrates.

Just beyond where we saw the jackrabbit we walked up a rocky dry streambed and Filigree Skimmers were flying up ahead of us and landing on the next big boulder. These are fancy tropical dragonflies that don't come very far north of the Mexican border. A field guide I read said that identification was "unmistakable because of the wing pattern alone."

Another much commoner but equally unmistakable species of dragonfly was the Flame Skimmer.

It was near the end of the season, so many moth and butterfly caterpillars had reached their full size before pupating. Here are two butterfly species poisonous because of eating poisonous plants, first the Queen from eating milkweed, and then the Pipevine Swallowtail, from eating pipevine.

In keeping with the harsh desert scene, in addition to the poisonous species there were a number of venomous species (a neat distinction to keep).

This first caterpillar, though the photograph doesn't show it so much, looked so much like a lichen growing on this branch that Cheryl and I both passed it by, until Gawain called us back and pointed it out to us. It's a subtropical species related to our Io Moths, and like the Io Moth has spines that can sting you and raise a nettle-like rash on you if you carelessly brush against it.

  The next is quite interesting and one we have long wanted to find. It's a Puss Moth caterpillar, the name obviously coming from its hairy coat and what looks like a tail. If you brush against this one, the effects can be quite serious. "Sensitive individuals," says Wagner, the writer of our caterpillar  field guide, "who begin to develop systemic symptoms should seek immediate medical attention." We have heard of deaths occurring.

 In the last couple of years we have been mainly interested in learning something about spiders as a group, so we were particularly paying attention to the spiders. Mostly we were seeing here desert versions of species we have at home in Arkansas.

This jumping spider for example we are certain is Phidippus clarus, a familiar species at home, but here seemingly twice as big with its wide pancake abdomen.

And everywhere we found Green Lynx spiders (handsomer with a paler pattern than ours at home) clinging protectively to their egg nests, which they will continue to do all winter until they freeze or starve. Spiders are often quite good parents.

Most abundant was the Labyrinth Orbweaver, a species also fairly common in Arkansas. It is best known for weaving two separate kinds of webs side by side. First it has a tidy and typical orb web, round in shape with spokes radiating around it like a bicycle tire. And then, a little bit over to the side, it has a chaotic tangle of lines with no order to it (the "labyrinth"); perhaps these two webs each catch specific kinds of insects. A few lines connect the two webs to each other, and in between the webs the spider weaves a few leaves together to make a little retreat it can hide in if it's disturbed. That's how it does it at home, anyway.  Here is a typical Arkansas set-up with the orb web in the background, the tangled web in the foreground, and the spider itself in between in its refuge.

But in Arizona they do something different (this is our first season studying them, so perhaps those in Arkansas will do this same thing only a little bit later than the Arizona ones). In Arizona I did not see them in a little leaf bower, but rather, they began laying egg nests. Here is the first egg nest.

Here is a second. They are laid in a line, with the spider at one end. Notice how the spider resembles the egg nests.

The spiders keep on doing it.

And I think I get what their dodge is. At this time of year the mesquite trees their webs are located in or under all have their seed pods drying and ready to fall to the ground. The least breath of wind and there is a rain of these tiny strings of seeds. Frequently instead of reaching the ground, they are caught in a spider web. I think a hungry bird coming along and seeing this juicy spider with its nourishing eggs might pass it by thinking it is only a dry and tasteless mesquite pod.

Postcript added 26 October: After a comment made about the egg nests of the Labyrinth Orbweaver, I made the mistake of doing a little research, and what I find is, that the eastern Labyrinth Orbweaver, such as I see in Arkansas, Metepeira labyrinthea, is not the same species as I have just written about in Arizona. In fact there are at least five different Metepeira species in Arizona (numerous other species throughout the west), and only the eastern one should be called a Labyrinth Orbweaver, though the others are nearly identical in appearance and nest building and egg laying. This is why, I suppose, the one I photographed in Arizona might mimic mesquite seed pods when there are no mesquites in Arkansas. Everything is so much simpler in the east.