Dragon fly bcoz it can be use in experimental studying due shorter life span ,or for more refer NCERT class 12 book

it is a bio control agent which feeds on mosquitoes

because it is a pollinating agent like bees

how are humans beneficial? every living thing has its own purpose. now, to answer your question, drangonflies in the insect foodchain, stand somewhr on top of the chain. they help in reducing the mosquito population. some asian dragonflies can even eat spiders from their webs! and an amazing fact,, the dragonfly nymph breaths through its anus!! ikr, gross! but, to it, it also serves as locomotion. it takes in water through its butt(its a water creature initially) and then expels it out after taking in the necessary gases. this also provides it with a propulsion and gets a "weird" locomotion. lol! anyway, hope this helped you! all the best!! :D

Dragonflies control the pest population. They help take care of biting insects that can be hazardous to human health as well as insects that can harm vegetation.