84 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 105 



the basal plate with a distal sclerotized crossbar and median fusion of 

 the endomeral projections as in S. cephalosus (Denny) . The remaining 

 species, exemplified by S. stemae, form a group that seems to have very 

 little in common with the remaining members of the genus, and seem 

 to be the only group that has shown extensive speciation among the 

 terns. 



The differences between many of the species are minute, and often 

 can only be expressed in quantitative terms. An example of this is 

 shown by the separation of the males of S. laticaudata and S. brevi- 

 comis. All measurements and chaetotaxy counts, except for the width 

 of the clypeal signature and the number of setae on the sixth abdom- 

 inal tergite, do not show valid statistical differences when subjected 

 to the "t" test. No attempt has been made to erect subspecies for 

 species such as S. petersi, where a good series of specimens was avail- 

 able from three host subspecies, as no valid statistical differences could 

 be obtained for any character or combinations of them. 



Measurements of the type specimens are listed in table 5. Certain 

 of the measurements prove to be diagnostic for the separation of 

 species. These are summarized in tables 6 and 7. 



In the key to species in Clay's paper, the symbols for "greater than" 

 and "less than" were reversed and the name vittata was used in the 

 female key instead of lockleyi. Corrections have been made in the 

 keys below, and several additional species have been included. 



Key to species of Saemimdssonia j 



Males ! 



1. Basal plate with distal sclerotized crossbar 2 



Basal plate without distal crossbar 3 



2. Cephalic index less than 1.04; length of paramere less than 0.24 mm. 



lobaticeps (Giebel) 

 Cephalic index greater than 1.05; length of paramere greater than 0.28 mm. 



hopkinsi Clay 



3. Endomere with terminal, strongly sclerotized, toothlike process. 



melanocephalus (Burmeister) 



Endomere with terminal, lightly sclerotized, evenly rounded process; or 



lacking one 4 



4. Paramere less than 0.15 mm. in length ... . parvigenitalis new species 

 Paramere greater than 0.20 mm. in length 5 



5. Linear arrangement of mesosomal setae (occasionally clustered on one 



side) 6 



Clustered arrangement of setae on both halves of the mesomere .... 10 



6. Inner face of paramere head with basad concavity (virtually forms a right 



angle with shaft) 7 



Inner face of paramere head with slight basad convexity 9 



7. Paramere greater than 0.33 mm. in length .... meridiana Timmermann 

 Paramere less than 0.31 mm. in length S 



i 



