orchard spiders   2 comments

what when where pic
orchard spider, leucauge venusta 2010, mid April through early September bushes in front of house

The last time we mentioned orchard spiders , we talked about their visitation in 2009. They came back, and they were awesome!

For some reason, the bushes around the front of our house seem to be a little paradise for orchard spiders to flourish in. I don’t see them in this kind of profusion anywhere else. Wonder why? The Blue Hills, for example, are the province of the Linyphiidae — haven’t seen any Tetragnathids there, to the extent that we’ve looked. At Purgatory Chasm, we find House Spiders, Linyphiids, Agelenids and the occasional Tetragnathid, so more variety, perhaps? We did notice orchard spiders on a reservation in Cape Cod late in the year. I don’t immediately see a pattern that would describe what the orchard spiders need to be successful.

First signs were visible around mid-April. Around this time they were tiny: perhaps a couple of millimeters? Their webs were found in the bushes at this time, to better fit the small size of the webs. As the spiders grew, the webs would move to larger and more distinctive locales. She’s not very shy, our Leucauge.

The spiders themselves grew rapidly. As they did, evidence of moulting was visible:

From wildlife20100424

Around May 1, they still had that distinctive red curve that long ago gave me a little frisson with the idea that we may have black widows. They seem to lose the rouge as they grow older.

From wildlife20100424

In this next photo, we can distinguish the hairs on the fourth pair of legs. We can also see the chelicerae, which are frankly a little disappointing in their size. The family is, after all, supposed to be the Long-jawed Orb Weavers.

From wildlife20100424

The next few photos lead to some rather wild speculation on my part. This speculation was launched by three separate observations. First, look at the shape of this particular spider. Doesn’t she seem a little distorted?

From wildlife20100424

Second, look at this disgraceful web she’s weaving. It doesn’t seem like an orb web at all.

From wildlife20100424

The third observation is that I’ve seen wasps near the spider’s location, seemingly patrolling with intent.

The best explanation for these observations is that there’s nothing unusual happening. First, the spider was her normal self, or perhaps pregnant, was not actually misshapen in any way. Second, the fact is that orchard spiders normally build irregular “foundation” webs below their pretty orb webs, similar to the webs of house spiders. Perhaps this is a means of providing extra security from attack from below? And third, flying is simply what wasps do, and it don’t mean a thing.

But what’s the fun in that explanation? There’s a possible turn of events that’s much more dramatic. We know (thank you again, David Attenborough) that there are wasps that lay their eggs inside the bodies some species of spiders. According to the venerable “The Spider Book” by John Henry Comstock, this certainly does happen to Leucauge Venusta. Isn’t it possible that the burgeoning wasp babies would distort the shape of the host spider? We also know that at the very end, spiders which contain these cute little wasp babies forget how to spin orb webs, leading to some pretty messy webbing. This is enough to make me wonder. I certainly wasn’t able to decide between either explanation based on observations, although I tried. Maybe next year.

Anyway. The orchard spiders that I could observe did flourish. I believe that these are egg sacs, witnessed on May 8, 2010. Although you can’t see the web very well in these photos, I did notice plenty of flotsam and jetsam also suspended in the web — I would guess as camouflage for the egg sacs.

From wildlife20100424
From wildlife20100424

All photographs heretofore have been females, I believe. Here’s a male, as deduced from his thinner body and longer legs. I guess the male’s legs are longer to help in copulation, but don’t know. But there’s an interesting point: why are nearly all the orchard spiders that I see, female? Are the males wandering around? Are they getting eaten by the females?

From wildlife20100424

This next photo was taken May 30, 2010. The spiders are much larger now, one to two cm, and you can see that the red swerve has faded completely. The webs are quite large, maybe 50 cm. In spite of the large size, it’s not unusual to see two webs next to each other. I’ve never seen these spiders interacting with each other.
You can see the hairs on the fourth pair of legs much better in this photograph.

From wildlife20100424

Here’s an orchard spider trying to hide from me. Futile, really.

From wildlife20100424

In the middle of August, I could see the results of this fecundity. There was the next generation of orchard spiders, 1 or 2 mm in size, back on the bushes where the previous generation had its start. So how many generations a year are there? And what of winter? What happens if one generation is just half grown by the time it gets cold? At the same time, I don’t see the previous larger ones any more. Are they dead of natural causes or are they too tempting as targets, with their bright coloration and conspicuous webs?

EDIT: Early October, and the little ones are still around, in their little webs. Would love to see how they overwinter.

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2 responses to “orchard spiders

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  1. Congratulations on being the Number 1 blog on the Nature Blog Network and not being from ScienceBlog. I look forward to new observations!

    Take care!

    Purple Carrots and Fairy Smoke

    • Thank you! I enjoy writing these notes, and am glad that you do too. The page-viewing traffic will fall from this absurd level, but watching the world outside remains fun.

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