The Australian Museum has lots of information. Here's some -
Grasshoppers, locusts, crickets and katydids belong to a group of insects known as orthopterans (meaning 'straight wings').
Grasshoppers and locusts have a row of pegs like a comb on their back legs. They scrape these pegs against the hard edges of the front wings to make sounds. Crickets and katydids produce sounds by rubbing their wings together. In order to hear these sounds, orthopterans have a tympanum (ear) on each front leg, just below the knee.
Locusts and short-horned grasshoppers belong in the other suborder, Caelifera, and have shorter and more robust antennae.
Locusts and grasshoppers (Suborder Caelifera, Family Acrididae) are very common insects. However, locusts behave differently depending on their numbers. When numbers are low they act as individuals, in the same way as grasshoppers. But when large numbers are present they behave as a group or swarm, causing plagues.
I did a grasshopper collection at uni and I only include pretty grasshoppers. It took many hours wandering aimlessly with my net to catch enough to make the collection - but I can't remember how many that was. All I remember were the hours to collect, then the yelling at me (by my Mum) when jars of grasshoppers filled the back fridge - because I hated using chloroform to kill them and thought freezing to death was more humane (go figure).
Okay, I need the critter to open his wing for good identification - see these photos are just no good. I should be collecting the critters!