This is something that I actually posted on another site first, but it fits here, so I'll post it again. I'm too lazy to write this again, so I cut and pasted. One other person on the other site seemed to think this was interesting, and maybe somebody will here too. I hope that cutting and pasting from another site does not violate some rule of internet etiquette, but here goes:
As a disclaimer, I am a total newbee, am not a chemist, do not yet own a single bee, and I do not know what I am talking about. (I do have various hive parts put together and have ordered some bees.)
That being said, here is an interesting thing that I came across, from two totally different sources.
I have a 1976 edition of The Hive and the Honey Bee, and in a topic relating to "Fanning" behavior, it states that in "orientation" or "scent" fanning bees release chemicals from the Nassanoff gland to attract other bees. It states that the chemicals released by the gland include "gerianol, citral, nerolic and geranic acids," and possibly other unidentified compounds.
Here's the interesting part. I have a book titled On Food and Cooking (2004 edition) by Harold McGee. This is not a cookbook, but is a food science book for laypeople. (Really great book if you are interested in that sort of thing and the 2004 edition is a major update.) The On Food and Cooking has a chapter on the chemistry of herbs and spices that includes a summary of the importanct chemical compounds contained in various herbs and spices. According to Mr. McGee, the compounds in lemongrass that provide its flavor profile include: citral, gerianol and linalool. Citral and gerianol are two of the chemicals made by the Nassanoff gland. Frome the name, I suspect that gerianic acid, which is also secreted by the gland, is similar chemically to gerianol.
Lemon Verbena contains citral and linalool, but not gerianol.
However, bees may like Linalool too, since it is contained in several other herbs that bees like, including basil, lavender, tarragon, marjoram and thyme. A member of my bee club actually puts a few drops of marjoram oil in her sugar syrup, and she says the bees really like it.
According to McGee, some of the chemicals that make herbs and spices flavorful are really just ways that plants deter animals from eating them (maybe including thymol, which is the main but not not the only chemical in thyme). However, I think that some of these chemicals apparently exist to attract honeybees. The plants appear to have evolved (or, if you prefer, were designed/created -- please don't start that debate) to produce chemicals that bees produce to attract each other.
Moreover, this may mean that lemongrass oil contains at least two of the primary chemicals that bees actually make to attract other bees. Maybe buying bee pheremone is not much (or any) better than just getting some lemongrass oil.
Just my two cents.