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

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., d can- homyops species), the .species is plotted as an X at the extreme, left (Fig. I) if nocturnal only, one position farthe.rto.the' right; if out 296 Psyche [December as late .assunrise, another position to the right; etc.As far as pos- sible, only summer records were used so.as to make directly com- parable.
It can be seen that the species in Acanthomyops, in Formica, and in Cataglyphis are closely grouped within each genus.The species in Lasius appear less so, but they barely overlap those of Formica or Cataglyphis. (NONE)

McCluskey
Generic Diversity 297 Scoring an X in the letmost column o Fig.
as "", next to the let ("night") as ":", and inally the rightmost column as "5", Thus the likeness within genera is greater than that between genera.

McCluskey
Generic Diversity 299 and Williams' (956; cf.Batschel,et 965, but only ]?or a two- sample case) test" i? the.samples are considered random, F_, _ 3.58 and P < .05 [N 33 (species), q 4 (genera), R refers to the, combination vector ]or all the species in each genus, and R refers to. the com- bination vector o]? all genera].Figure 2 .
shows that ]?or the three genera o.] this tribe with enough species records, the flight hours o]7 the species within a genus are strikingly similar, exceptions being the one morning species o] Lasius and the two a]?ternoon species o]? Formica.Comparison o]? the flight hours by the Watson and Williams test again shows the.likeness within genera to be greater than that between genera.(P .oo).
It seems noteworthy that a single rhythm character would char- acteriz,e a genus this well.A preliminary test or generality o. the within-genus likeness o]? flight hour was made on eleven genera ]?rom five subfamilies o]7 ants (all o.]? those ]?rom which liter, ature records of at least three species per genus were at hand).The Watson and Williams test gives a value o]? P < .oothis is.true also i]? the three ormicine genera are omitted and only the other eight considered.
By including all species records no.matter what tribe, it is pos- sible in a few cases to rank workers from early to late within each given locality (McCluskey, unpublished).Again species appear grouped generically, giving ]?urther suggestive evidence o]? a taxo- nomic or historical explanation o.] the phase differences (as opposed to a strictly ecological or geographical explanation).
An example of a physiological character earlier shown to correlate well with a previously-established classification is that by Priesner (968).Male moths throughout the family Saturniidae were shown to react to pheromone from the ]emales in a manner roughly cor- responding to taxonomic grouping.
It should be added that some o]? t'he phase relationships, considered here might in a.ct be expl.ainedby response to temperature', since these are records ]rom the field rather than a constant temperature laboratory.But this consideration does not change the fundamental nature o]? the conclusion drawn.Further, certain ants which have been studied in constant temperature exhibit a phase relationship to the light cycle similar to that in the field (McCluskey 963, 965, 969 McCluskey and Carter 1969).

SUM,MARY
Literature records of field mating flight and worker rhythms in- dicate the phase to be much more alike ]rom species to species within Psyche D ecembe a genus than between genera.The analysis is based on about a. third o the world species in each o several genera o the tribe Formicini.
Comparison in more genera, &om several subamilies, again indicates this prominent within-genus likeness o behavior.

Fig. 2 .
Fig. 2. Flight ho,urs.Each F represents for one species the halfway paint between the earliest and lates.tliterature records of flight; () indicate the most fragmentary records.The following are represente,d: FORMICd: