My Little Mosquito Tree

My little mosquito tree,
Much it cares for me,
Keeping away dengue!
Its services I don't see
Yet my house is mosquito-free.

...............................
Notes

1. While difficult to see tangible results from "preventive measures" or "services", its worth is felt and appreciated only in contrast to the manifestation of the thing that it prevents.

2. Thus, the benefit of services like insurance and wills become apparent when certain contingencies take place, e.g. a testator dies intestate (without a will) or a man is struck by terminal illness and he has not enough funds for healthcare.