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Misumena, Misumenoides, and Mecaphesa

Lynette's recent question sent us back to the books and the images stored in BugGuide. Here is our admittedly amateur answer to the question of identity of these three. Please advise where this should be posted once people have had a chance to add comments and after we fix this draft.

Misumena:
All four anterior (front) eyes are about the same size. When viewed from the front, and a little above, it seems all eight eyes are visible and form a crescent shape. The lateral eyes are on tubercles, but the posterior laterals are visible. See



Misumenoides:
All four anterior (front) eyes are about the same size. When viewed from the front, and a little above, only six eyes are visible. The posterior laterals are facing sideways and are on the ends of a long horizontal transverse ridge across the face. See



Mecaphesa:
The anterior lateral eyes are a little larger than the anterior median eyes. When viewed from the front, and a little above, only six eyes are visible. The posterior laterals are facing sideways and backwards on tubercles that include the anterior laterals. Mecaphesa is also often (always?) hairy. See



Comments, corrections, and suggestions most welcome.
john and jane

Mecaphesa/Misumenops
Mecaphesa and Misumenops are difficult to distinguish from each other (except by genitalia) but they can be distinguished from similar crab spiders (north of Mexico) as follows:

(1) They always have robust macrosetae on the carapace both around the eyes and posterior to the eyes, extending at least halfway back. The larger the specimen, the proportionately smaller the setae, but the setae remain present and robust. Misumessus females, Misumena vatia, and Misumenoides have much less conspicuous carapace setae.

(2) The pattern of robust setae on the carapace is consistent from individual to individual but has an irregular appearance on any individual. This contrasts with Misumessus males, whose carapace setae have a more evenly-distributed appearance as well as an appearance of more consistent lengths.

(3) The abdomens of Mecaphesa and Misumenops are always more conspicuously setaceous than those of M. vatia, Misumessus females, and Misumenoides.

(4) The ALEs are always larger than the AMEs, but sometimes not much larger.

(5) Mecaphesa and Misumenops tend to have medial and submedial dark maculae on the dorsal abdomen. They tend to be medial anteriorly and submedial posteriorly. It is rare for other crab spiders to have this pattern. The pattern is often characteristic enough to be diagnostic, but I don't know how to describe it diagnostically in text. Carapace patterns vary dramatically and may be absent.

(6) Mecaphesa can be found on flowers, on green vegetation, and in trees. Preferences vary by instar and species.

(7) Our only known Misumenops is M. bellulus in southern Florida and the Carribean. This group has a lot of variability in Mexico, so determination to genus gets less confident in the southwest. My habit is to assume they're all Mecaphesa until I learn otherwise. M. bellulus can have red markings -- but many Mecaphesa can as well, so I'm not sure how helpful this character is.

(8) Occasional Xysticus are similar to Mecaphesa. Xysticus have larger ALE/AME eye size ratios, while Mecaphesa have larger femur-length/carapace-width ratios. Males of both groups tend to have much longer first legs, but male Mecaphesa first legs still have greater femur/carapace ratios. The abdominal pattern is often sufficient to distinguish them.

NOTE: The 1st edition of the SNAIM (aka SONA) manual had an emphasis on relative eye sizes in a few families. A decision was made to remove dependency on relative eye sizes for the 2nd edition, because this was found unreliable across all examined families. I did my own investigation of relative eye sizes in thomisidae and found it mostly helpful but not diagnostic -- and in any case, I wasn't sure how to clearly communicate the range of relative eye sizes in a repeatable way.

Misumenoides
I use the following characters to identify Misumenoides from photos. Mind you, Mexico appears to have several species of Misumenoides, so we should watch for these characters in unusual-looking crab spiders in the southwest:

(1) All Misumenoides have a pronounced ridge (the "carina") below the ALEs and above the carapace margin. This is diagnostic. This ridge merges with the anterior margin of the carapace, but most crab spiders have a visible anterior margin, so look for the additional ridge below the ALEs. This ridge is usually white, less commonly yellow, and sometimes not distinctly colored. The common name Whitebanded Crab Spider refers to this ridge.

(2) Confusingly, most Misumenoides appear to have a distinct ridge between the anterior and posterior eye rows. It is also often white, but it is not diagnostic for the genus. Eye regions have a bit of variability among both species and individuals. Even so, when the carina is not clearly visible, this secondary character can be used as a contributing clue.

(3) Unlike most crab spiders, the adult female Misumenoides first tibia have only one or two ventral macrosetae at its distal end. If you see a tibia apparently devoid of ventral macrosetae, it's likely Misumenoides.

(4) Misumenoides have a more angulate appearance than most crab spiders, particularly due to having ventrally flat femora and tibia.

(5) There is some overlap between the color patterns of Misumena vatia and Misumenoides formosipes, at least on the carapace and abdomen.

Misumessus vs Misumena vatia
The thomisidae comparison page needs some updating for Misumessus and Misumena vatia:

(1) Misumena vatia ALEs are sometimes distinctly larger than the AMEs. Alex Wild has a gorgeous photo of one such M. vatia, and I've seen several specimens where they ALEs are definitely larger if not much larger. However, M. vatia ALEs and AMEs are usually about equal in size. (Edit: This M. vatia has ALEs much larger than AMEs.)

(2) Misumessus ALEs are always larger than the AMEs, though sometimes not much larger. The Misumessus ALE/AME ratio can be identical to the Misumena vatia ALE/AME ratio for some specimens. Significantly larger ALEs usually indicates Misumessus, but not always (see above).

(3) Misumessus abdomens are usually but not always reticulated with green or white guanocytes, while M. vatia abdomens are usually without but not always without reticulated guanocytes. Not a reliable character.

(4) Misumena vatia carapaces can have dark (green to brown) submarginal bands. Misumessus apparently never has these carapace submarginal bands.

(5) Misumena vatia and Misumessus can both take pale color forms in tints of tan, green, yellow, or white. However, it appears that when M. vatia takes one of these tints, the same tint can be found on both the carapace and the abdomen. Carapace and abdomen can be more strikingly different in color in Misumessus. When the abdomen is brightly colored and the carapace pale, likely Misumessus.

(6) Both Misumessus and Misumena vatia can have red/pink dorsolateral bands on the abdomen. Given observations so far on BugGuide and iNaturalist, it appears that if the bands are broad or strongly dorsally arched, it's Misumena, though this is not a requirement for M. vatia. If the lateral bands are anterodorsally connected, likely Misumessus, but iNat shows a broad dorsal swath on one specimen of M. vatia and an anterior connection on another. However, per this specimen, it appears that the red band need not connect in front on Misumessus. Misumessus abdomens can also have pink, red, or dark colors dorsally, especially males. This certainly applies to Misumessus lappi, may apply to other Misumessus as well.

(7) Misumessus abdomens are often yellow laterally while white or pale green dorsally. I don't know if Misumena vatia abdomens can have this pattern, but the stronger this color difference, the more confidence we can have that it's Misumessus. However, if the dorsal abdomen shows two paramedial bands slightly darker than the surrounding color, it's probably Misumena vatia, which often shows this in immatures, sometimes in adult females, always darker in adult males.

(8) Some all-white or all-yellow female specimens of Misumessus and M. vatia cannot be distinguished except by examining genitalia. I had a dozen of each genus under my microscope looking for consistent, distinct morphological characters other than genitalia and was not able to find any. Here is an example of an all-yellow one that could be either Misumena or Misumessus.

(9) Misumessus lappi can easily be distinguished in both males and females from M. vatia and other Misumessus by its projecting nose -- the anterior-most carapace projects past the anterior margin of the carapace. See here.

(10) A minor clue that's only helpful for confirming or disconfirming other clues is that Misumessus is usually found on green vegetation, including trees, while Misumena vatia are more often associated with flowers, at least as adults.

For many specimens, I think we'll be acquiring confidence in the ID by accumulating noticed characters, rather than by pointing to single definitive characters.

(Updated 15 July 2018 for improved understanding of Misumena vatia color patterns. And again on August 8 for all-yellow Misumessus/Misumena.)

Misumessus
So what about Misumessus?

 
Misumessus
Great eye shots added by Joe here.

 
more eye shots
I am late to the party on this, but captured a Misumenoides formosipes the other day and took some decent shots of the eyes:



I have added one of the thumbnails to several of the relevant guide pages.

 
Just found this
Thanks so much for the work put into this!

 
We and Lynette just learned that one
this summer. It was split out of Misumenops. We're not sure of the eye details that might make it different from Misumenops. Not even sure that some of the images we called Misumenops aren't actually Misumessus! It will have to wait till we learn more. Oh! for an expert in Misumenops!!

This is a great reference
I had missed the link to it on the family page before, but found it after John and Jane identified a Misumenops of mine just now. It seems to me that this should all appear on the Thomisidae page, rather than being hidden on the Misumena vatia page. I was tempted to just copy and paste it right now, but figured I'd better comment here instead, in case there was a reason for its placement that hadn't occurred to me.

Edit: I see now that this is also on the Misumena genus page, but the link below took me to the Misumena vatia page. I think the most logical approach would be to have the comparison occur at the family level, and then just show the genus in question on the page for each genus, stressing the defining characters, and referring users to the similar genera and/or back to the family page in the "see also" section. I think the genus page is also the best place to offer tips on distinguishing among members of that genus, as I have attempted to do here. The M. vatia page ought to highlight what is distinctive about that species, and it seems odd to have the comparison of the genera repeated there.

I'm just trying to articulate the organization scheme that most helps me personally when trying to sort out an ID--if anyone feels differently, please chime in!

 
Crab spider
Hi! I was wondering if this spider poses a danger to humans or cats or dogs? There was one on our deck step and it was quite pretty. Of course the neighbor killed before I can say stop. But, is it toxic at all? Thanks for any information. I did see THE book on insects everyone has been ordering and plan on ordering one myself. But I need to know soon if this poses a harm, if not I will have everyone refrain from killing it. Thanks again!

 
99% of the time the answer to your
question about any spider is No! The only spiders that you are wise to avoid are the Widows and the Recluse. You can find images of those two here in the guide. Any other spider, the answer is no. Is this one dangerous? No. Is that one dangerous? No. How about the one over there? No. You have two to watch for - Widow and Recluse. Please spread the word to your friends and neighbors.

 
One advantage to having it at the species level
users unfamiliar with the taxonomy are more likely to find themselves at that info page than at higher levels, if they come to the guide via an image or an identifying comment. I don't see any harm in showing the same information at many levels of the guide.

 
My two cents
Just stumbled across this thread belatedly while looking for crab spider info.

Generally, when information that logically belongs at a particular level is copied onto multiple levels, it can cause confusion. The example I notice most is when species pages have the "numbers" field filled out, e.g., "three species in this genus," which always makes me think I've somehow ended up on a genus page.

 
Yes
This continues to be an issue, and I recently made a post about it here. To Hannah's comment above, I would respond that editors should remember to make use of the "see also" section of guide pages.

Moved to guide page
We moved this to the Identification box on the Misumena guide page here, and linked to it from Misumenoides and Misumenops. Please continue to make comments and corrections here and we will make those changes there. Now that we have done this we have questions on Richard's and Tony's . They seem more like Misumenoides to us. What do others think?

This is great.
As you may have noticed, I've been floundering about with only a very vague notion of the differences based on a single comment in Florida's Fabulous Spiders!
Either a link to this, or the whole thing, should be posted in the identification section of each of the relevant guide pages, I think.

 
I agree.
Yesterday I linked some good forum discussions to the Peucetia guide page.
Any relevant discussions in the forum pages should be utilized.

very nice
The one line about there being six eyes visible vs. eight is a great help to me. Thanks for this!

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