In Australian English, the nouns grasshopper and its shortened form grassy, typically used in the plural, denote a tourist, especially a visitor to Canberra *, as opposed to a permanent resident. The image is that a coachload of tourists is similar to a swarm of grasshoppers.
* Canberra is the capital of Australia and seat of the federal government, in Australian Capital Territory, an enclave of New South Wales.
The earliest occurrences that I have found of the nouns grasshopper and grassy used to denote a tourist are as follows, in chronological order:
1-: From Column 8, by ‘Granny’, published in The Sydney Morning Herald (Sydney, New South Wales) of Thursday 8th June 1950:
Commercial travellers call bus tourists grasshoppers—“they arrive, eat and depart.”
2-: From The Argus (Melbourne, Victoria) of Wednesday 9th January 1952:
They’ll have to walk
Girls who ride into Canberra on motor-cycle pillion seats in future will have to “walk home.”
And some who have just arrived will have to walk, too.
The A.C.T. Road Council recently banned pillion riding.
Since the ban, Canberra police have “taken a lenient view” of breaches, though they have warned some offenders. None was prosecuted.
But now all that’s to stop.
The annual influx of “grasshoppers” (Canberra’s words [sic] for tourists) has included many motor-cyclists, some of whom have brought girls on their pillion seats.
Mr. Kent Hughes, Minister for the Interior, said today: “Even where there has been no prosecution the girls’ fate will be the same—they’ll have to walk home.”
3-: From Capital Talk, by E. H. Cox, published in The Herald (Melbourne, Victoria) of Friday 1st August 1952:
Canberra, Fri.—This week provides a reminder that in public affairs one year’s meat is another year’s poison.
Members in Canberra next week will find one striking indication that Australians are not spending nearly as freely as a few months ago.
What the House attendants call the grasshopper plague has nearly vanished.
The grasshoppers are big waves of bus-borne tourists who, in the past four or five years, have visited Parliament House in quotas well up to 200 a day.
Hotel accommodation in Canberra is much easier than for almost a decade, and it has again become possible for locals to get fairly prompt service at garages.
4-: From Harold Cox’s Canberra Comment, published in The Sunday Mail (Brisbane, Queensland) of Sunday 3rd August 1952:
Fewer tourists visit Canberra
A drastic diminution of the numbers of what Canberra a little unkindly calls “Canberra grasshoppers,” is just one of the current signs that Australians are spending a lot less freely than a few months ago.
The “grasshoppers” are the bus-borne tourists who since the war have flowed into the city in ever increasing numbers.
An imaginative attendant at Parliament House aptly coined the name from the avidity with which they descend on a particular spot, absorb all they can of sights and facts, and then migrate to another interesting area of the city.
A few months ago anything up to a dozen buses might trundle up to Parliament House in a single day to disgorge its load of sightseers.
Now the average of organised visits is probably not much more than one bus load a day.
5-: From Canberra Attracts Many Tourists, Too, published in The Sydney Morning Herald (Sydney, New South Wales) of Saturday 3rd September 1955:
Probably the biggest tourist attraction in Canberra is Parliament House. Tourist coaches unload swarms of “grassies” (grasshoppers) outside the main steps every few hours, and guides show visitors through the building.