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[Vol. 90 
Table 2. Types of S. chamberlini intermorphs according to Plateaux’ classification 
of Leptothorax nylanderi. 
Source 
Form 2 
Form 3 
Form 4 
Form 6-7 
Total examined 
Wheeler (1904) 
0 
1 
5 
0 
6 
Colony no. 1 
3 
1 
4 
2+) 
10 
Colony no. 2 
7 
0 
13 
2++) 
22 
Colony no. 3 
2 
2 
13 
0 
17 
■'■)Both with thoracic sutures and sclerites according to Plateaux’ form 7, except for 
the lack of wings. One specimen with very short forewing rudiments. 
■*^)Two specimens between Plateaux’ form 6 and 7, without traces of wings. 
mainly in that class of intermorphs. It is worthy to stress that Holli- 
day’s (1903) data for 1000 specimens of L. provancheri includes 37% 
of intermorphs without the microgynes; the intermorph composi- 
tion exhibits the same trends as in chamberlini. 
The karyotypes cannot yet confirm a closer relationship of all 
these guest ants. However, they also do not contradict such an 
assumption. F. nitidulus has a haploid number of n = 15 chromo- 
somes, L. provancheri has n = 1 1, and S. chamberlini with n = 14 
lies in between. For F. hirticornis and diversipilosus the chromo- 
some numbers are not yet known. 
Summing up the known features, queen polymorphism with alate 
and intermorphic females, males with their tendency to reduce 
wings and to become ergatomorphic, the presence of inseminated 
young (and in Formicoxenus also old) potential queens in the nests, 
and the life habits as guest ants, we believe that Symmyrmica, and 
also L. provancheri, should be incorporated in the genus Formi- 
coxenus. A comparative morphological study has been undertaken 
in order to link the biological informations accumulated on the 
guest ants mentioned above in a taxonomic revision of the genus 
Formicoxenus. 
Acknowledgements 
We thank Karl Fischer for providing the chromosome number of 
Symmyrmica chamberlini, and Robert Loiselle for laboratory 
assistance. Wheeler’s specimens were loaned by the American 
Museum of Natural History, New York (Mrs. A. Favreau), and by 
the USNM, Washington, through Dr. D.R. Smith (USDA). 
