. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. North American Ptomaphagus ⢠Peck 149 â hirtus "cluster"- loedi ngi "cluster". shapardi nicholasi hirtus ti ubrictiti volenti nei hiazelae loedi ngi solcnum loedi ngi Julius loedingi longicornis loedingi loedingi barri episcopus hatctii hatch! hatchi fecundus whiteselli fisl<ei waiter i 3 o o 3 3 o def i ni te cave i solation 215 Figure 215. Hypothetical diagram of specific diversification in the hirtus group of the subgenus Adelops. See text for explanation of possible periods of alternating c
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. North American Ptomaphagus ⢠Peck 149 â hirtus "cluster"- loedi ngi "cluster". shapardi nicholasi hirtus ti ubrictiti volenti nei hiazelae loedi ngi solcnum loedi ngi Julius loedingi longicornis loedingi loedingi barri episcopus hatctii hatch! hatchi fecundus whiteselli fisl<ei waiter i 3 o o 3 3 o def i ni te cave i solation 215 Figure 215. Hypothetical diagram of specific diversification in the hirtus group of the subgenus Adelops. See text for explanation of possible periods of alternating cove restriction and overland dispersal. Degree of specific difference not inferred. hirtus group, from the primitive zone as a general forest litter inhabitant into an obligate inhabitant of the zone of deep (montane?) forest litter. As they became specialized for this second adaptive zone, liirttis-group members became preadapted (in the sense of Mayr, 1963: 593) for the cave occupation which occurred later in the Pleistocene, just as Barr (1965, 1967b) proposed for the cave occupation of trechine carabid beetles. When did the cave occupation occur? Only three observations lead me to believe that the hirtus group did not invade caves before or after being forced to by the drying-warming trends of the Sangamon interglacial. All the cave species have eye remnants. I think these would have dis- appeared if the cave occupation had been in the earlier Yamiouth or Aftonian inter- glacials. Secondly, I would expect surviv- ing montane populations of ancestral de- scendants if the cave occupation had been early in the present interglacial, but none have been found. Lastly, range sympatry does not exist and it might be expected to occur from additional dispersal opportuni- ties if the initial cave invasion was in the Yarmouth. Within the hirtus group, there are two distinct clusters of troglobitic species (Fig. 215). One, the hirtus cluster, is composed of nicholasi, hirtus, and hub
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