Phoresy is a zoological term, really an entomological (insects) term. Phoresy is when a large species of insect carries about smaller ones tucked in the wings or riding piggyback. It's when the smaller species of bugs "hitch a ride". A very kind and benevolent thing to do if you were to see bugs as having needs and emotions. I suppose other animals could do it. Why not? The difference between phoresy and parasitism is that parasites are detrimental to the health of the host.
Consider this parable about faith: When Jesus says that our faith, as a grain of mustard seed, will grow to become a tree, "so that the birds of the air come and lodge in the branches thereof" (Matthew 13:32), it's like He's talking about a sort of spiritual phoresy. I mean, when you think about it. Or maybe I'm extending this parallel too far because a tree's not an animal. But you get the idea. Think about this for a second: If this parable is a blanket statement, in that it applies to every Christian with faith, does this mean God will eventually expect us to host "the birds of the air"? Meaning anyone God brings across our path who can't, for whatever reason make it on their own, spiritually? If we've never thought of this question, maybe it's because our faith is not there yet? God help us.
"The foxes have holes, and the birds of the air have nests; but the Son of man hath not where to lay His head." (Matthew 8:20)
Jesus showed us how to do it: "When I was with them (His disciples) in the world, I kept them in Thy name: those that Thou gavest me I have kept, and none of them is lost" (John 17:12). Except Judas Iscariot, it says. God the Father trusted Jesus with the care and tutelage of His disciples. God had complete faith in His Son. Jesus expresses the same sentiment to us when He says to "go ye therefore, and teach all nations" (Matthew 28:17).
Before we can go into all the world to do this though, the church on the homefront must practice what is being preached. Paul wrote to the Galatians that they should "bear...one another's burdens, and so fulfill the law of Christ." (6:2) Paul also spoke of "travail[ing] in birth again until Christ be formed in you" (Galatians 4:19), meaning that he was seeing them through the spiritual (godly, of course) vision-quest needed to gain hold of Jesus for themselves. What Paul is saying is if we truly know Jesus and are strong in our faith, then we should be asking God to bring to us those who aren't where we are so we can see that they get what we got. "Him (and her) who is weak in the faith receive ye" (The first part of Romans 14:1). Has God blessed you with any spiritual "mobility"? Can you jump from one place to another easily without any difficulty? Do you have no fear or trepidation for your needs and those of your family? Then take some time, however God leads you, and do the same for others. The second part of Romans 14:1 says "but not to doubtful disputations". Paul qualifies his plea, for spiritual phoresy, if I may, by telling those in the position of responsibility to not nitpick about doctrinal differences that are immaterial and neither here nor there.
In closing, a simple contrast: don't confuse phoresy with Pharisee. Jesus dealt with them. They flatly refused to help other people: "For they bind heavy burdens and grievous to be borne, and lay them on men's shoulders; but they themselves will not move them with one of their fingers." (Matthew 23:4)
And I do love bugs!