Yeah, get that under control reasonably quick- especially if you see ants around. Ants herd aphids kind of like cows- feeding off of a bodily secretion they produce (its either the secretion of the moldy soot that results, I don't remember for sure- either way, aphids=cows). Aphids in and of themselves are not that big of a deal other than making your plants look horrible and acting as vectors for diseases like nasty fungi and such- they are generally easy to control. The problem; however, is that ants also herd mealy bugs which are a huge problem and very hard to completely get rid of. Mealy bugs can get down into the root system and start sucking juices down there. No bueno!
As far as treatments go,
- I have successfully used neem oil on my sarrs.
- I know that soap sprays are not usually suggested (and I respectfully acknowledge NaN's warning here), personally I have used both a home made dish soap solution and potassium salt based commercial spray on my sarrs without a problem. Soap sprays are incredibly effective on aphids across the board (more effective than neem oil). When in doubt, I usually wash the soap spray off after 10 minutes or so. I have found that with sensitive plants- this helps.
- Ladybugs are hit or miss on CPs. VFTs usually chomp on them.
- I have also successfully used Imidacloprid based systemic insecticides on my sarrs and found that they do ok with it (only tried it once). I just sprayed the leaves- not the crown. Don't use that on droseras. You will regret it... I speak from experience...
To give credit where it is due- some of these ideas I got from this video by Jeff Dallas (check out the fungicide one too):
http://www.youtube.com/watch?v=lbRCdJ8ZNF0
Others from experimentation and/or books. One book I am currently experimenting with is "Protect Your Garden: Eco-Friendly Solutions for Healthy Plants" by Ed Rosenthal. That book does leave a lot to be desired in terms of background information (IMO) but is handy nonetheless.
If you guys come up with other treatments you find effective (for any species of CPs), I put together a section of my website dedicated to pesticides and fungicides which are found to be both effective and safe for different species of CPs. I would appreciate any input you can provide (Eventually, people will be able to add such data directly.... close to that but WIP).