1985] 
Thayer — Mieralymma 
53 
strongly modified in males than females, and those on the male pro- 
tarsi are more distinctly flattened than those on the other tarsi. Most 
species of Omaliinae, if possessing flattened tarsal setae at all, have 
them only on the protarsi (sometimes also mesotarsi) of males 
(Thayer and Newton 1979; author’s unpublished data), presumably 
aiding in grasping females during mating. The distribution of the 
specialized setae in M. marinum is very much like that found in 
omaliine genera whose adults are flower-inhabiting pollen feeders 
( Eusphalerum , Pelecomalium, Amphichroum, Austrolophrum, and 
Anthobiomimus). In both cases it seems to be an adaptation facili- 
tating adhesion to the exposed surfaces on which the beetles occur 
(see Stork 1980, 1983), with the more pronounced development in 
males again presumably related to adhesion to females during 
mating. 
King et al. (loc. cit.) mentioned the pupa of M. marinum as 
having “a number of long lateral setae . . . which presumably also 
help in maintaining position” in rock crevices. These long projec- 
tions (not actually setae) are found in all described omaliine pupae 
( Olophrum , Paulian 1941; Antarctotachinus, Jeannel 1940; Brathi- 
nus, Thayer 1985) and Microedus (author’s unpublished data). Of 
these, all but Brathinus have pairs of similar projections parame- 
dially on the abdominal tergites as well. (Laboulbkne 1858 illus- 
trated the pupa of M. marinum but apparently overlooked the 
dorsal projections.) 
Lindroth (1931, 1957) proposed that Mieralymma marinum orig- 
inated in North America and that its trans-Atlantic distribution 
resulted largely through passive transport of beetles by the Gulf- 
stream, attached to pieces of seaweed, driftwood, or other flotsam. 
This explanation does seem ecologically, physiologically, and 
meteorologically plausible (Laboulbfcne 1858 and Elliott et al. 1983, 
immersion tolerance data; Lindroth 1931 and 1957, map of Gulf- 
stream), but another factor that must be considered in analyzing the 
historical biogeography of the species is its phylogenetic relation- 
ship to the other species of the genus: where might the common 
ancestor of M. marinum and its sister-species (or sister-group) have 
occurred? As this phylogenetic question has not yet been explored, 
the question of why Mieralymma marinum is where it is must be 
regarded as only tentatively answered. 
