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What eats large fishing spiders?

We have six-spotted fishing spiders, _Dolmedes triton_, in our lily pond; some grow quite large. Several times last summer, I found dead ones which had been "unhinged" by a predator that ripped off the "lid" of the cephalothorax and ate the contents, leaving the legs attached to the sides of the cephalothorax and abdomen attached behind. From the location of the remains (usually on top of waterlily leaves, including leaves elevated above the water) the predator would have to have been above water level (?? or maybe I found only the ones that were left that way??) In one instance, the "lid" of the cephalothorax was still attached on one side, open just like a box lid. Field guides just tell me what the listed spiders eat, not what eats the spiders. Someone suggested to me that herons feed on these spiders--does anyone know for sure? Could they be neat enough to just open the box and eat that part?

On a lighter note, the other day I watched a water strider and a fishing spider face off...the spider was on a water lily leaf (with two feet in the water) and the water strider had headed for a gap between that leaf and another...and then paused. The spider edged farther off the waterlily leaf; the water strider slid away, then back; the spider retreated a little. This went back and forth while I took pictures. It was all very slow but very intense. I have a picture of that up on my website this week (along with other spiders) at http://www.sff.net/people/elizabeth.moon/photogallery.htm.

Another answer:-)
I agree with the Balaban's diagnosis of the shed exoskeleton, but I also wanted to mention that some spider wasps prey on Dolomedes spiders. Namely, Tachypomplius will tackle Dolomedes tenebrosus away from water. There is another spider wasp in the genus Anoplius that will actually pursue some Dolomedes underwater! Check out Howard Evans' classic book, "Wasp Farm" for the discussion.

 
Lots more to learn...
...like the scientific names of our local wasps. Right now I have no idea which of the elegant creatures prey on spiders. My background's primarily botany and applied ecology; I'm just getting started with the insects & spiders (invertebrate zoology class was a long, long time back for me.)

I appreciate all the help--thanks!

Another question: can you recommend a good basic book on insects/spiders, including taxonomy? I'm used to using botanical keys and not just field guides for plants; at present I'm finding the insect/spider field guides annoyingly uninformative on relationships. I have 80+ acres to prowl and catalog; I'd like to be able to work up a local checklist and visitors' guide that showed critters in their taxonomic relationship.

Elizabeth

 
Bug keys, taxonomy
For taxonomic relationships you can't do much better than this gigantic list here on bugguide!

For a key-based insect guide you might do well with "How to Know the Insects". Like any other single publication, it doesn't describe every species of every insect, but it hits quite a few and will usually (always?) get you to genera. Hopefully someone else can attest to this book's value. I own it, but have gotten very little use out of it since my main interests are with jumping spiders.

For spiders I would recommend "Spiders of Connecticut", but only after comparing the Connecticut list with Texas to make sure there's enough overlap to be valuable to you. It's an excellent resource. 1020 pages, with over 2300 drawings and photos (mostly drawings). Each species is accompanied by a paragraph (usually two or three) describing it's physical characteristics, and the habitats and dates in which they have been collected. Only place I know of to purchase this one online is at the State of Connecticut Department of Environmental Protection website.

There's also a nice online 'beginner' key walk-through for spiders at Black Rock Forest. I say beginner because each step is very well-illustrated and easy to follow.

All of these references will get you to genus with almost all bugs that you run across, and all the way to species in many cases. This might be good enough for you if you are mostly concerned with order and relationships.

If you need to ID to species you have to be aware that holes exist in all general references, and make sure you don't just match your mystery bug to the closest species description. (spiders are notoriously difficult, even for a properly equipped professional) Lucky for us, you can find a lot of very detailed keys online in various places. Try adding your favorite genus or family name to the beginning of this search and see what fun things you can come up with.

 
Taxonomy...
Thanks!

"Need" to ID to species is...probably not critical, except that I'm finicky. If I can key forbs and grasses to species, then I expect (of myself) to be able to key everything else to species, too. May be unrealistic, but I really would like to have a checklist for this acreage that is accurate and as complete as humanly possible.

I'll definitely check out your recommended publications--if I can get things down to genus level, that will help a lot.

Thanks for the warning about just matching my finds to the closest picture/description in a book. I may already have done that for some wasps. I've got Drees & Jackman's _A Field Guide to Common Texas Insects_, which was disappointing (generally bad picture quality, incomplete lists, and at least one outright error), the Audubon general field guide for insects and spiders, Abbot's excellent guide to Odonata of Texas and surrounding states, and quite a few butterfly books.

Elizabeth

 
We're all eagerly awaiting
Eric's book! You can place your order at Amazon now!
Kaufman Field Guide to Insects of North America
by Kenn Kaufman, Eric Eaton (Paperback - January 12, 2006)

Not yet released.
List Price: $18.95
Buy new: $12.89

 
Aha! Book-ordering time!
...though where we're going to PUT the books I now feel I must have, I dunno.

Thanks for the recommendation.

Elizabeth

 
I don't know about books, but
This website has some excellent resources. The guide is arranged like a tree, with the broadest category (arthropods) as the trunk and each subgroup as a branch. That means that if you're looking at a particular critter and want to know what's related to it, you can just click on the broader category that includes it (the "parent") and see what other "children" it has.

As for books, each guide page has a Book tab, which has entries people have submitted telling about books they know. The entries start with books associated with that guide page (if there are any), then to the parent pages, and so on, until they get to just general books on bugs.

If you wanted to find a book on moths, for instance, you would go to the guide page for moths and click on the book tab to see what book entries people have submitted.

I've only been hanging around here for a few months, so I'm still finding useful features that I didn't even notice.

 
I'm learning....
....I've only been on this site a few days, and already like it a lot, but I'm also floundering around a bit. I know I'll catch on more with time...sorry if I seem impatient. It's just the combination of a ferocious curiosity and knowing I have limited time.

I do appreciate the time people are taking to help me ID critters and navigate around here.

Elizabeth

Sounds like the spider unhinged herself!
Check out Richard's fabulous to see an Argiope doing it. Spiders must shed their exoskeleton to grow. If you just found the empty shell, it may simply be a molt by the owner.

 
Utter amazement...
I certainly never thought of that! How cool, and what an incredible picture! Next time I see one of the "husks", I'll find a way to retrieve it and see if there's any meat in the legs or abdomen...that would, I guess, be the thing to look for.

Did anyone else think "octopus" when they saw that picture of the Argiope sliding out of its exoskeleton? I know, they're cephalopods, not arachnids, but there's an eerie resemblance right at that point. To me, anyway.

Thank you for the insight.

Elizabeth

 
If you're thinking octopus --

 
I'm so glad...
...I'm not a spider. I once got stuck in a tight-fitting dress with one of those old-fashioned under-the-arm zippers and a tiny zipper at the neck...this whole spider molting thing looks like it would be just as unpleasant for the spider.

Great pictures, though.

Elizabeth

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