Read mǎ in the very common 蚂蚁 ('ant'). Switch to mà for 蚂蚱 ('grasshopper') and to mā for 蚂螂 ('dragonfly', dialect). Three readings, all in the same insect family.
The insect radical on the left marks this as a small crawling creature; it stays the same across all three readings, since ant, grasshopper, and dragonfly are all bugs.
Supplies the sound on the right: 马 mǎ gives the base reading, which shifts tone to mà or mā in other compounds. It contributes no 'horse' meaning here.
