Arachnids’ head and thorax are combined into a cephalothorax. There is no way to separate just the head.
Arachnid orders I’ve photographed so far
Order Sarcoptiformes
https://inaturalist.ala.org.au/observations/265531461
Order Trombidiformes
https://inaturalist.ala.org.au/observations/149504222
Order Holothyrida
https://inaturalist.ala.org.au/observations/104698663
Order Ixodida Ticks
https://inaturalist.ala.org.au/observations/85427703
Order Mesostigmata Mesostigs
https://inaturalist.ala.org.au/observations/168032709
Order Araneae Spiders
https://inaturalist.ala.org.au/observations/111354214
Order Opiliones Harvestmen
https://inaturalist.ala.org.au/observations/68618168
Order Pseudoscorpiones Pseudoscorpions
https://inaturalist.ala.org.au/observations/75464041
Order Schizomida Shorttailed Whipscorpions
https://inaturalist.ala.org.au/observations/104695351
Order Scorpiones Scorpions
https://inaturalist.ala.org.au/observations/79263044
Order Solifugae Solifuges
https://inaturalist.ala.org.au/observations/171506830
Order Uropygi Whipscorpions
https://inaturalist.ala.org.au/observations/51205731
The ones I have left to find are
Order Opilioacarida
Order Palpigradi Micro Whipscorpions
Order Amblypygi Tailless Whipscorpions
Order Ricinulei Hooded Tickspiders
Arachnids are definitly one of my fave groups of organisms. My first guide book for a specific group of organisms (besides dinosaurs) was a Collings Gem for spiders of the world. Which I got when I was around 11. In recent years, as much as I love all arachnids harvestment has been my main focus.
In terms of behaviour, its always fun to watch courtship. Last year I got to spend a while watching a Syntrechalea? male presenting a nuptial gift to a female (And eventually getting turned down).
Besides this first image, this is a small sequence of the approach, though focus is pretty out in general across the scence of the images. https://www.inaturalist.org/observations/256607324
This is still one of my fave spider and prey shots.
Dolomedes dondalei
https://www.inaturalist.org/observations/146948813
Whilst its very common to see fishing spiders fishing. This is the only I have shot which has caught a fish. You may need to look at the larger image to really take in the fish under it.
Im really not sure on the genus of this next one. But its another prey on water that I thought looked pretty cool.
https://www.inaturalist.org/observations/255861246
I also quite liked this scorpion somehow holding onto a much larger prey
Tityus gasci
https://www.inaturalist.org/observations/255061917
One of my current aims is to get top 10 by species for harvestmen/opiliones. Currently I am only 23rd.
When living in an oldish house in the mountains of central Italy, one morning I was fascinated to find the aftermath of a deadly battle which had taken place during the night. If someone had asked me, I would never have believed the Pholcus phalngioides would have had the better over quite a large and decidedly well-armoured Euscorpius.
If you have an issue to discuss, I think it would get more attention if you make it a stand-alone item on the Nature forum rather than burying it in here. Not many people will search through all these spider photos to see if there is a discussion somewhere. The longer this gets, the less likely they are to look.
Not really issues, more of a general place for people to talk about spiders, their behavior, etc
We get lots of marmorated bugs here, and I’ve read that jorō spiders eat them. The closest recent (and most recent close) observation of a jorō spider was in Mill Spring last year, and there are three others last year only slightly farther away. There was one in Chimney Rock State Park in 2021, but no one’s going there until they fix the roads. Am I likely to see a jorō this year?
Hopefully! Good luck!
Nice topic! Before 2021, I would never have thought I’d have a favorite arachnid, much less a list of them, but thanks to iNaturalist, I do. Like @Thunderhead’s, my arachnophobia is also easing as I seek out observations and strive for better photos of what I see. The variety of colors, patterns and even expressions you can see when you zoom in is amazing. I currently have 586 observations of 126 species of arachnid (good job, self!). Some of my favorites are:
Of the 3 times I’ve seen pseudoscorpions, 2 were examples of phoresy 
Salticidae (Jumping spiders)
These spiders can have beautiful colors, like the shiny pink above, and even blue as shown recently in the blue organisms thread (WOW!). They strike funny poses, seem to wave a friendly hello, and assume adorable pensive expressions. One of the most interesting things I got to see was when 2 males had a battle. I didn’t stay to see the end result, I wasn’t ready to witness what might happen, but I got a series showing the match.
I also really like the Micrathena spiders.
Micrathenas are very tiny, and are hard to get the camera to focus on (at least for me), but when you manage it (try using a mirror, it helps!), you get to see their crazy shape, beautiful patterning, and their lovely web structure! 
(Edit: the right-most picture of the Micrathena gracilis I got by holding a mirror under the spider and taking a picture of the reflection, since I was unwilling to try to crawl under and look up. (-: )
A cool spider I found recently:https://www.inaturalist.org/observations/266516736
It’s surprising how much sexual dimoprhism spiders display. This is the male of the same species:https://www.inaturalist.org/observations/266516873
So today’s question is to see some of your observations of arachnid dimoprhism !
Alternatively, how about some shiny metallic spiders?
And then there is spider sociality. Depite me having the first (and so far only) observation in the region, Anelosimus studiosus is common here, especially noticeable when the trees are bare because their communal webs hold masses of dried leaves. Tying this into the earlier comment on dimorphism, this species is socially dimorphic, with some living in groups in communal webs and sharing brood care, while others live solitary and are territorial. The two types are interfertile.
I am a fan of the various spiny orbweavers. I certainly want to try and clock up more of these species https://www.inaturalist.org/projects/spiny-orbweavers-gasteracantha-and-kin?tab=species
Pseudoscorpions is also something I want to work on improving my macro of.
One of my fave (older images) of dimorphism
Ornamental Tree Trunk Spider Herennia multipuncta https://www.inaturalist.org/observations/36148950
Unfortunately quite grainy for this Golden Silk Spider
https://www.inaturalist.org/observations/182031076
The female is in the center of the photo, the male is near the top:
Trichonephila clavata | Joro Spider · 무당거미 | Observation
Argiope aurantia (Yellow Garden Spider) sexual dimorphism
Philodromus marxi (Metallic Crab Spider) sexual dimorphism and metallic (woohoo! poor photos though…waaah…)
This shiny male was soo thrilling to see, and that thrill combined with his apparent desire not to be seen, made it challenging to get decent pictures of him…he was fast
The female was missing legs, but was still fast…
Weirdly, I’ve discovered in doing this post, I saw the male on June 17, 2022 and the female on June 17, 2024! So I guess I know who to look for on June 17th this year!
It actually is not but something cooler.. a kleptoparasite living in the web of the nephilid 
Sounds like Philodromus is aptly named!
Oh, really! I had no idea! Sorry about the misidentification.