I was reading this question about a soft bullet thereby getting inspired to think of how to deliver a fake insect sting. I want it to leave as little bruises as possible, to resemble a sting and nothing to remain in the wound. Ideally, it would look like someone was stung by an insect. That would be the advantage to just shooting a needle.
When I drive in a car and the car decelerates, I continue flying forward, unless I wear my seatbelt. Suppose I have a very soft bullet filled with one or several needles facing in (exactly or nearly) forward direction, loosely tied to the back of the bullet. Could the needles upon impact continue moving in the direction of motion, slightly come out of the squeezed bullet and deliver a fake insect sting? The idea is that after the sting the soft bullet falls off, pulling the much lighter needle out of the wound.
Probably the terrible aerodynamics of a soft projectile would not permit long ranges. But perhaps it's enough if the tip is soft.
How thin a needle would be theoretically possible, if I had very hard materials available? Obviously only very thin needles can leave stings delicate enough to be mistaken for the doing of insects.
To provide for more inertia, the tip of the needle could be very fine, while the body could be somewhat thicker. It would still have to be light compared to the bullet. Furthermore, I suspect it would have to be fine tuned to a very narrow distance range.
Let's first not focus on tricking experts! Whether it works is the main question. Imagine a world where poisonous insects sometimes occur. A man is killed using the correct venom. At worst it will take time before anyone looks at the sting with great detail.