66 
Psyche 
[June-September 
the gaster predominantly smooth and shining. Variation in the queens 
is poorly known because not many of the “ unidentata” workers are 
accompanied by females in the collections I have seen. In general, 
loaisianae - complex queens have stronger gastric sculpture than the 
workers accompanying them. 
In view of the discordant nature of the variation in the only good 
distinctive characters available, I am forced to consider fusca, uniden- 
tata, and clasmospongia as synonyms of louisianae. It is possible that 
the variation of this very plastic species is even greater in central and 
northern South America, from which our samples are so few, and per- 
haps even the large, very long-mandibulate producta is only another 
extreme variant of louisianae. The type of fusca does show tendencies 
in the direction of producta, but we shall need more material from 
Western Brazil and Bolivia before we decide this question. Of course, 
the possibility must not be overlooked that louisianae really is made 
up of a number of cryptic species, inseparable by conventional mor- 
phological study. 
A fact of continuing interest is the absence of S. louisianae from the 
forest on Barro Colorado Island in the Panama Canal Zone. Inten- 
sive collecting by a number of mvrmecologists on the Island was re- 
peated in January i960 by Dr. E. S. McCluskey and myself, making 
full use of Berlese funnels and other modern collecting techniques, 
but no one has yet found 5 . louisianae on the Island or elsewhere in 
Panama. This is especially strange in view of the fact that the species 
is common in banana plantations on both the Atlantic and Pacific sides 
of Costa Rica near the Panama border (El Palmar and Coto in the 
Golfo Dolce, E. O. Wilson leg.). While we now have very inade- 
quate ecological information, it does seem possible that S. louisianae 
may be a species that has adapted to habitats marginal to the rain 
forest of the South American continent, and that this has something 
to do with its present wide distribution — the widest of any New- 
World dacetine. In this sense, S. louisianae may fit Wilson’s (1959) 
“Stage-I” category of expanding species. It is also of interest to note 
that the species is much less variable (“more typical”) in the North 
American extremities of its range than in the presumed evolutionary 
center in South America. Furthermore, the “typical” characteristics 
of short mandibles and reticulate gastric sculpture, while discordant 
one with the other geographically, tend to prevail at the extremities 
of the range in North America and South America as well, indicating 
a centrifugal evolution and movement of these characters. 
Below r I have listed some of the available samples of S. louisianae 
by geographical regions, with special emphasis on some of the more 
