Commensal Relationship between Spittlebug nymphs and Fly larvae

On the underside of several leaves, I found small masses of "slime" containing 1 or 2 Spittlebug nymphs each. No froth, although some bubbles are visible (pictures 1 and 2). No adults nearby unfortunately. The slimy exudate of the nymphs was sticky. I picked up one on my fingernail to get a closer picture and to my surprise found a fly larva next to the nymph (pictures 3 and 4). Both were moving around and did not seem to be bothered by the presence of each other. As the slime dried out, the two snuggled close together to stay moist (pictures 5 and 6). I don't think this is a parasitic relationship, as both seemed healthy and only interested in sharing the slime. There is a parasitic wasp (Family Dryinidae) that parasitizes Spittlebug nymphs, but the larva is visibly attached to the nymph and is dark in color, as well as smaller and shorter. There is also an interesting study about the commensal relationship between Spittlebug nymphs and Drosophila larvae. Neither species seems to affect the other or result in smaller Spittlebug adults or smaller flies. See: https://www.researchgate.net/publication/271795012_Spittle_Maggots_Stud…. The larvae however do benefit from the moist environment the Spittlebugs provide.