Dragonflies are found worldwide. They have four elongated wings, a mouth, two short antennaes. #when adults emerge as speedy terrestrial fliers, they begin breathing through a network of tracheal air tubes and live only for a couple of weeks. They eat small insects including small frogs. #When nymph (baby dragonflies) can't find food they use their antennae from the top of its head to find food.
The giant dragonflies of ancient earth with wings span of up to 7 centimeter (28inches) are generally attributed to higher oxygen atmosphere levels in the atmosphere in the past. In raising modern insects in various oxygen enriched atmospheres have confirmed that dragonflies grown bigger with more oxygen, hyperoxia.
Why: these changes happened may be in the hallow tracheal tub insects use to breathe. Getting better handle on those changes I modern insect could make it possible to use fossilized insect as proxies for ancient oxygen levels.
How: the term raised cockroaches, dragonflies, grasshoppers, worms, battles&other insects in atmosphere containing different amounts of oxygen. In result, was that dragonflies grow faster into two biggers adults in hyperoxia. However, cockroaches grew slow and did not become large adults in size in lower oxygen atmosphere.
Life cycle: #dragonflies lay there eggs in water. #nymphs then span some time in the water to continue it's metamorphosis #once nymphs shed their skin, they spend rest of their life out of water.
Characteristics: #back in the Carboniferous period the wingspan of dragonflies we're 76cm, now there about 2.5cm. #dragonflies get their body temperature fro their environment. #wingspan determines their size.
Where: vanderbrooks of arizona state university in Tempe, research presented nov. 1at geological society of American's annual meeting in Denver, Colorado.