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[Vol. 95 
Table II. Representative shifts in distribution. 
1. st. davids head: 1973: megacephala and humilis coexisting; 1986; 
humilis only 
2. mullet bay road and 1963: P. megacephala only (sparse); 1966: humilis 
ferry road and megacephala — shifting lines with greatest area 
(st. George’s island) occupied by humilis; 1973 mixture of humilis and 
megacephala; 1986: I. humilis only 
3. Leamington caves 1963: I. humilis only; 1973: Area where P. mega- 
cephala has replaced I. humilis; 1986: /. humilis 
only 
4. KNAPTON HILL INTER- 
SECTION 
1963: I. humilis only; 1973: P. megacephala 
apparently replacing /. humilis; 1986: I. humilis 
only 
5. KNAPTON HILL ROAD AND 
HARRINGTON HUNDREDS 
1963: I. humilis only; 1973: Area where P. 
megacephala has replaced I. humilis; 1986: 
/. humilis only 
6. christchurch/brighton 
HILL 
1963: Mixture of P. megacephala and /. humilis; 
1973: Area where P. megacephala has replaced /. 
humilis; 1986: I. humilis only 
*7. SPITTALL POND RESERVE 
8. HAMILTON-NEWSTEAD 
9. WRECK ROAD 
*10. IRELAND ISLAND 
1963: P. megacephala only; 1973: P. megacephala 
only; 1986: P. megacephala only 
1963: I. humilis only; 1973: /. humilis only; 1986: 
Predominantly /. humilis, but with small inter- 
spersed colonies of P. megacephala 
1963: Mixture of I. humilis and P. megacephala; 
1973: New Iridomyrmex focus, bordering on area 
of /. humilis and P. megacephala; predominantly 
I.- humilis; 1986: P. megacephala only 
1963: P. megacephala only; 1973: P. megacephala 
only; 1986: P. megacephala only 
*Of the ten localities recorded, only these two (Spittall Pond Reserve and Ireland 
Island) have remained unchanged (both with P. megacephala only) throughout the 
twenty-three-year observation period. 
In sum, these accumulated results would seem to give a fairly 
highly probable answer to the questions posed in 1965: the situation 
would seem to be one of equilibrium rather than slow replacement, 
at least on the time-scale involved. 
Certain ancillary observations are of interest. Despite the near- 
saturation of the environment by the “tramp” species, other ants 
have regularly been reported, often now as cryptic rarities, in all of 
