locust, locus

Locust or locust means the insect, a type of grasshopper that can swarm in great numbers --
The locust can still swarm and devour crops, just as in ancient times.
That's not a locust; it's just a grasshopper.

Locust or locust also means a type of tree, or the wood or seeds of one of these trees  --
There is an old locust tree on the corner; you can't miss it.
Carob powder is made from locust beans.

Locus or locus means a place or position --
This test may determine the locus of the nerve damage.
The rally became the locus of controversy, although it remained peaceful.

Now that you know that, you can say --
"The scientists would like to find the locus of the original locust, the beginning of the swarm."

Note --"locusta" means a spike that grows from grass --
If the grass grows tall enough, you will see a locusta shoot out of it, like a spike.

Note #2 --"lochus" means a body of soldiers in an army of Ancient Greece --
A lochus of his men were still waiting to ambush the enemy scouts."