Breathable warm-weather pants?

I think eVent would be FAR too warm. The lowest abrasion fabrics would be something like lycra, or maybe silk. You can get very light, very quite, very soft silk pants…I wear lycra shorts under may pants/shorts to prevent chafing and they work a treat, but they're not as cool as a loose fitting fabric.

My favorites are REI Sahara and Ex Officio.

Have a read of the BPl article on bushwhacking trousers. The Taslan fabric might be a very good choice. – better than EPIC for sure.

Cheers

You might also want to check out the Railriders Eco mesh pants. I've used them a lot lately down here in the desert and really like them. A good combination of light and durable, with zippered mesh side panels.

http://tinyurl.com/6jhsdd

I have an older version of these that I noticed have been re-introduced …… you can't tell much from the photo but they have a mesh inseam panel that's several inches wide and runs from the crotch to within a few inches of the cuff.

http://www.exofficio.com/product_details.aspx?item_cd=1121-5009&key=46c55028-033b-4200-a632-e910b82655cb

Here in Scotland i wear a pair of Montane Terra Lite pants in summer. They are very breathable, have a water-resistant finish and mesh backed thigh vents. Only 310g/11oz. I don't know if you can get them in the US.
http://www.montane.co.uk/productdetails.php?productid=64&rid=1

Like Andrew King I'd recommend a look at the Rail Riders Eco Mesh trousers. The only fault I have found is that the design could do with an additional rear belt loop to stop the belt riding high over the waistband, but I just sew one on from fabric scraps (or, most recently, from the fabric sample included in a Hilleberg tent catalogue!)

The material is pretty tough (it survived miles of Scottish heather-bashing with nary a pluck, while my friend's North Face trousers came out looking like Velcro) and the zips on mine have proved reliable; I bought them six or seven years ago.

I'll second the Montane Terra Lite recommendation. Durable, breathable, zippered side vents, Cordura reinforced
knees, bottom, and inside ankles; All in all a great pair of pants, on trail or off. I'm still on my first pair 4 years later. Only down side is inseam length/waist combos are limited. A medium waist, which I needed, came only in a 32" inseam. Problem is that I needed a 30" inseam. Shortening them turned out to be a not so trivial operation, as the ankle zips had to be moved up accordingly or sacrificed. I won't divulge what it cost me, but suffice it to say I swallowed hard. No regrets looking back, though. One other thing: they are hard to find in the USA. I think you might be able to special order them through Prolite Gear now that they're carrying Montane products again.

Another vote for Montane Terra Pants. The side vents are great. I ordered them from a U.K. retailer (really costly, but totally worth the expense).

Montane Terra Pants are my trousers of choice for the last three years. Great, light, good features. I am tall so I got XL length, but have to tighten the belt a lot. So don’t be bothered about the inside leg length v waist size, they come with a belt. All in all you would struggle to find better trousers to hike in.

After wrecking several pairs of REI Sahara's and one other brand of zip-off's I switched to Rail Riders, so I'll second (third? fourth?) the Eco Mesh pants. I've also recently bought their Weatherpants for lower temps. Durable, perfect fit & utility. I have a feeling I won't be buying another pair of backpacking pants for a loooong time.

Arc'Teryx Palisade Pants and Railriders Weatherpants are the two toughest, non-cotton pants I've come across. The Arc'Teryx wins out slightly for some elements superb to the Weatherpant such as water-resistant zippered pockets, low-profile integral belt, et al.

I haven't worn the pants other people are recommending. Very light nylon can be tough and pretty breathable. But in my opinion, the stretch woven pants, like schoeller dynamic, are more comfortable and subjectively cooler than straight nylon. Straight nylon will dry much quicker but seems hotter. Nylon is tougher and more resistant to snags. I have the beyondfleece steel pants and they are very light feeling and comfortable even on a hot summer day. Nylon is way cheaper.

My concern about mesh on my pants is bugs. Bug protection is one of the primary reasons I would wear pants in hot weather. Can black flies get inside the mesh? Can mosquitos bite through?