Eris militaris (Hentz, 1845) Discussion

bronze jumper

Comments on May 25, 2007 Observation

Bev Wigney
45.1456, -75.6088
2

Submitted: June 2, 2007 at 6:52:57 AM MST

All of the following account took place on an old plastic lawnchair that is sitting in a small orchard at the edge of a woodlot on our farm. The chair is surrounded by mixed grasses, Meadowsweet (Spirea alba) and other vegetation. On 25/05/2007, a female E. militaris was observed perched on the back of the chair. It moved to hide behind the back slats when I moved in for a closer look and to take some photos. On 26/05/2007, I checked the chair and found a male spider wandering about on the chair. On 29/05/2007, I checked the chair and found a small silky nest spun between some kind of stick-like cocoon (presumably made by moths) on the underside of the chair. There was also a granular-coated, oval, cocoon-like structure incorporated into the nest, as well as a small, dark, barrel-shaped object. A male E. militaris could be seen hiding withing the nest. I failed to notice that there was a female, upside-down, hidden beneath a couple of the objects in the nest (this was discovered after examining the my photos a couple of days later). While photographing the nest, the male moved to the entrance opening to watch me (see photo that accompanies this report). After taking a few photos, I found another male E. militaris on a nearby apple tree. It rappelled off before I could take a photo. On 30/05/2007, I checked the chair and found an upside-down spider in the nest. I thought it must be the male and gave the nest a slight tweak to see if he was alive. The spider flipped over to reveal that it was a female spider (the one that had been hidden from view the previous day). It moved around in the nest and can be seen in one of the linked photos next to one of the granular cocoon-like objects). The female spider then rappelled to the grass beneath the chair. I set the chair back in place. Returning to check on her that evening, I found her back on the chair, but in a nearby silky refuge. On 31/05/2007, I checked the chair and now found a female in the second refuge, but also another female wandering around on the chair in the immediate area of the spider in the nest. I will continue to observe these spiders over the next while. Photos to accompany this observation may be found at the following URLS:
http://www.pbase.com/crocodile/image/79811144
http://www.pbase.com/crocodile/image/79811147
http://www.pbase.com/crocodile/image/79811149
http://www.pbase.com/crocodile/image/79811151

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Bev Wigney wrote on June 7, 2007 at 10:49:28 AM MST

Hi Jean - Thanks for that information about the caterpillar! As mentioned, the chair has many of the stick-like cocoons and some of these granular ones. I believe you could be quite right about the granular ones being made by some kind of caterpillar. Since posting my account, Don Buckle supplied me with an image of an E. militaris egg case and it doesn't resemble the granular ones, so they must be something else. I might see if there are any that haven't emerged yet and bring them to the house to keep in a jar so that I can figure out just what they are.

Jean Leclerc wrote on June 5, 2007 at 6:46:02 PM MST

Hi both of you!

It might not be of great help but there's a small caterpillar who makes that kind of casing before pupating. These are covered with small grains of sand. I have seen many of them emerging from the lawn and climbing on walls early in spring.

Well, that was my two cents. Great photos by the way!

Bev Wigney wrote on June 2, 2007 at 6:08:24 PM MST

Thanks, David. I've been doing a bit of looking around as well, but so far have not found anything much. I'm going to try to examine some of these little cases with my loupe and see what they might be. One of the females has a couple of these granular cases in her refuge and she sits beneath one of them. I should really get back over to visit "the chair" tomorrow to see if she's still there and take more photos.

David P. Shorthouse wrote on June 2, 2007 at 11:25:08 AM MST

Wow! That's quite a post! I read your blog post the other day too...sorry I haven't been in touch. I suspect the urn-shaped, caddisfly-like enclosures are the female's egg nests. Inside each is likely an egg case. When you stumbled upon a female in a silken retreat, by best guess is she was in the midst of laying yet another bundle of eggs then would later affix debris to the enclosure to prevent desiccation, parasitoids/preditors, give it some camouflage, etc. But, take all this will a large grain of salt. If these are indeed compressed egg nests with debris, how can there possibly be so many? I best do some digging in the books and reprints to see what I can find.