Only in the fall and that is not a regular occurrence.

During the season too. But they mostly "catch the breeze."

The reason I asked is because I have been fighting them for three months and it is driving me nuts. I keep spraying with insecticidel soap and they just keep coming back. I vac up around the area while they are outside drying off. I just can't understand why they keep coming back. I've sprayed evry five days. Sometimes they don't show up for two weeks. I'm wondering if I want to bring anything in next year. or I'm going to spray every other day for two weeks prior to bring them in. I have two seven foot hybiscus trees - they are a pain.
Another thought - are they mites?? they are dropping black dots - very messy - I don't remember that before.

Aphids can and do give birth to pregnant females, if my memory serves me correctly. Needless to say, they can reproduce rapidly.

So, all you need do is miss one female, and you still have a new generation on your hands -- err, plant.

I don't know how often you check back after you spray, but if you start doing so earlier, then squish or wash off the few that you see, you can get the upper hand.

I can't believe I missed any - I sprayed and sprayed - the plants were dripping like mad. But you never know. I'm almost ready to go back to chemicals.

Remember to spray under the leaves.

Datura, the Aphids that you knock off your plants are not returning, what you are seeing is a new generation of Aphids and you will see new gnerations quite often since Aphids produce live young almost as soon as they are born. Perhaps this web site will be of some help in understanding about Aphids.

Here is a link that might be useful: All about Aphids