they sound to me like there like the babes of what evers flying in the air our lads put some dog food down sat night the dogs never eat it by sun tea time there was little groups of daffodil yello tiny as you say catapillere so tiny i put it down to the commen fly that gets in the house and if your plants are indoor it could well be that make a solution of what soapy water and wipe the shitty things of, you cant do what you can with a normal house plant can you? put them in the bath with no water in and shower them so they have a good watering and knocking the little shits of just keep on top of it and good luck