I am preparing tons of smoothies for entering a certain biome. While I can get the other two ingredients reliably, aphid honeydew is something I'm not entirely sure where to look for. The most consistent place I found so far was on the south bank of the pond in the clover forests early in the morning, before the ants ate them all. I tried trapping aphids inside enclosures, but they were too stressed and would not produce honeydews.
In real life, if you remove an aphid when it's sucking on a plant, its mouthpart would detach from its body and got stuck on the plant, causing the plant to constantly flow "aphid honeydew" out of the small needle. (http://bio1152.nicerweb.com/Locked/media/ch36/pressure_flow.html , much like the sap collector in game) Scientists used to study the content of plant fluid using this technique. In grounded, I once shot an aphid on the back side of a grass and it did not fall onto the ground even though it was dead, and I thought that, if not a bug, was the developer's work of building in this mechanism. I wonder if the team can further build upon this phenomenon and give us easier access to "aphid honeydew" that did not pass through the animals gut. The grass/clover would keep pumping out the honeydew for a day or so and die because of malnutrition.