olfaction in coccinelids

Hello saneters 
I was wondering if anyone has any information on kairomonal or 
synmonal attraction of coccinelids to crop plants. Other predators 
and parasitoids have been known to be attracted to either the pest 
itself, its excreta, sex pheromone or plant damage. Has any such 
attraction been reported for coccinelids? Are there any plants that 
are highly attractive to coccinelid predators? 
Does anyone know of a Biological Control discussion group? Or 
anywhere else I can get ideas and help in this matter?

Thank you very much, Nada