Generic Diversity in Phase of Rhythm in Formicine Ants

Ants are abroad through most of the day and night. But the species composition of this 24-hour .patrol changes from one part the day to the next (Talbot I953; Wilso,n I97I). For example, in Michigan the maximum foraging activity of Lasius neoniger is at night, of Myrmica americana in the early morning and late afternoon, and of Formica pallidefulva nitidiventris in the middle o.f the day (Talbot I946, I953). Likewise the mating flights of ants occur at differe’nt hours for different species (Kannowski 963 Talbot 1945). The flight times may be similar for clo.sely-related species (Kannowski I959a). If one were to look at many species of o.ne genus, would he find them to be similar as to time of da.y of f.oraging o.r o.f mating flight ? Or does each genus span the 24 hours in terms of its various species ? The aim of this report is to quantitatively compare s,pecies dive’rsity with generic diversity of such phase relationships in one tribe of ants, the Formicini. The biosystematics of much of this group, particularly of the genera Lasius, dcanthomyops, and Formica, is relatively well known o.n morphological and zoo,geo.graphic grounds (Wilson and Regnier I971 ). The comparisons are based .on a compilation of literature records. for as many species and genera as possible in this tribe (Figs. and 2). A genus was included if there were records for three o.r more. species. About a third o.f the species of dcanthomyops, of Cataglyphis, o.f Lasius, and o.f lyrmecocystus are represented in the records cited here, but a smaller fraction o.f the large ge’nus Formica’. These genera are all from North Temperate latitudes. (For a preliminary report see McCluskey, I972.) The workers could be classified as nocturnal, diurnal, etc. But in the absence of single or definite beginning points, or midpoints of activity in most of the literature records, another method was used t.o reduce e.ach rhythm to one point for comparison with other species" If the ants do not normally come above ground at all (e.g., dcanhomyops species), the .species is plotted as an X at the extreme, left (Fig. I) if nocturnal only, one position farthe.r to. the’ right; if out