cene); Schossnitz in Silesia, Krottensee in Bohemia and Rott in the Rhinelands (Upper Oligocene); Radoboj in Croatia, Falkenau and Kutschlin in Bohemia and Cape Staratschin, Spitzbergen (Lower Miocene); Sicilian amber and the beds of Brunnstatt in Alsacia (Middle Miocene); Oeningen in Baden, Parschlug in Styria, Tallya and Thalheim in Hungary, Gabbro in Italy (Upper Miocene); Sinigallia in Italy (Pliocene). The age of the North American deposits has not been accurately determined. Ants have been seen in the amber of Nantucket (Goldsmith, 1879) which is attributed to the Tertiary. Other

FIG. 90. Female of Lonchomyrmex heyeri, a Myrmicine ant from the Radoboj formation. (Mayr.)

FIG. 91. Worker of Rhopalomyrmex pygmæus from the Baltic Amber. (Mayr.)

localities are Green River, Wyoming; White River, Colorado and Quesnel, British Columbia, which are referred to the Oligocene, and Florissant, Colorado, which is said to belong to the Miocene.

The Baltic and Sicilian ambers and the beds of Radoboj, Oeningen and Florissant have yielded far and away the greatest number of ants. The most beautiful specimens are those of the amber, which are often so perfectly preserved that they may be as readily studied as recent ants mounted in Canada balsam. Most of these specimens are workers and belong to more or less arboreal species, but there are also quite a number of males and females. As nearly all of the latter have wings. they must have been caught in the liquid resin just before or after their nuptial flight. The preservation of the Oeningen, Radoboj and Florissant specimens is very inferior to those of the amber. The deposits in these localities are lacustrine, that is, they consist of fine sand or volcanic ashes laid down in fresh water lakes. This accounts for the fact that nearly all the specimens are males and females, for as Heer says: "With few exceptions only winged individuals are found, because the wingless individuals, in this case the workers, were drowned less frequently than the others. Both males and females occur, but the former are much rarer than the latter, probably because the females, having a

much larger and heavier abdomen, fell into the water more often than the males." The fossil ants of Florissant show the same peculiarities, except that the males are not much rarer than the females. Thus the condition which Le Conte interpreted as indicating an absence of the worker caste during Miocene and premiocene times, is easily and naturally explained. It is strange that he failed to see this, especially as in the paragraph immediately preceding the remark above quoted, he calls attention to the following interesting resemblance between modern

lacustrine conditions and those which must have prevailed at Oeningen: "On Lake Superior, at Eagle Harbor, in the summer of 1844, we saw the white sands of the beach blackened with the bodies of insects of many species, but mostly beetles, cast ashore. As many species were here collected in a few days, by Dr. J. L. Le Conte, as could have been collected in as many months in any other place. The insects seem to have flown over the surface of the lake; to have been beaten down by winds and drowned, and then slowly carried shoreward and accumulated in this harbor, and finally cast ashore by winds and waves. Doubtless at Oeningen, in Miocene times, there was an extensive lake surrounded by dense forests; and the insects drowned in its waters, and the leaves strewed by winds on its surface, were cast ashore by its waves."

The conditions described by Le Conte for Lake Superior are common to all our Great Lakes. The insects drowned in them are often buried in the sand of the beaches and might eventually fossilize, but

the Tertiary lakes of Oeningen, Radoboj and Florissant must have been much smaller, shallower and calmer bodies of water, and the insects that dropped into them or were swept into them by streams, were probably imbedded in the mud under water. Many of them were, of course, devoured by fishes. Professor Cockerell has sent me from Florissant several specimens of fossil fish excrement consisting almost entirely of the hard indigestible heads of ants. It is very unfortunate for the student that so few of the workers of the Oeningen, Radoboj and Florissant ants have been preserved, for our knowledge, as we have seen, is largely based on the worker caste and the males and females even of recent forms are so imperfectly known that fossils of these sexes are very difficult to classify, especially when the characters of most taxonomic value, such as the shape of the head, mouth-parts and abdominal pedicel are obliterated by flattening and distortion. Another great difficulty is encountered in attempting to correlate the

males, females and workers of the same species. This is no easy task with carelessly collected recent ants, but with fossils, except those of the amber, it becomes almost impossible.

The ants of Oeningen and Radoboj were first studied by Heer (1849, 1856, 1867) before the taxonomy of recent ants had been placed on a firm basis by the researches of Mayr. It is therefore impossible to assign most of Heer's species to their proper genera, and although Mayr (1867b) was able to examine a number of the Swiss paleontologist's species, he did not have access to the types. Hence the whole ant-fauna of Oeningen and Radoboj must be reinvestigated by some one thoroughly acquainted with the recent ants. The species

of the Baltic amber have been studied in a masterly manner by Mayr (1868a). A few additional species from the same formation were subsequently described by Ern. André (1895a) and Emery (1905e), and the latter has also described fourteen species from the Sicilian amber (1891e).

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According to Handlirsch's list of fossil insects, of the 600 species of Hymenoptera that have been described from the Tertiary, 307 or more than half are ants. These insects must therefore have been very numerous in individuals, just as they are to-day. This is true alike of the Baltic amber and the shales of Radoboj, Oeningen and Florissant. Mayr examined 1,460 ants from the amber, Ern. André 698 and through the kindness of Prof. R. Klebs, of the Royal Amber Museum of Königsberg and Prof. W. Tornquist of the Königsberg University, I have been able to study nearly 5,000 of these beautiful specimens. Heer says: The ants are among the commonest fossil animals of Oeningen and Radoboj. In the latter locality they predominate even more in proportion to the other insects than they do at Oeningen. Altogether I have examined 301 specimens, representing 64 species; from Oeningen 151 specimens of 30 species, from Radoboj 143 specimens of 37 species and from Parschlug 7 specimens belonging to 4 species." According to Scudder (1890), "the ants are the most numerous of all insects at Florissant, comprising, perhaps four-fifths of all the Hymenoptera; I have already about four thousand specimens of perhaps fifty species (very likely many more); they are mostly Formicidæ, but there are not a few Myrmicidæ and some Ponerida." I have recently made a rapid preliminary study of the 4,000 specimens of the Scudder collection belonging to the Museum of Comparative Zoology, and of nearly 3,000 more found at Florrisant by Prof. T. D. A. Cockerell, Mrs. W. P. Cockerell, S. Rohwer and myself, and am able to confirm Scudder's statement. There are probably not more than 50 species in both collections, many of them being represented by a great number of specimens, and hardly 70, or one per cent., of the 7,000 specimens are workers.

Of the described Tertiary ants that can be unmistakably assigned to their respective subfamilies, 139 species are Camponotinæ, 25 are Dolichoderinæ, 85 Myrmicinæ and 27 Ponerinæ. A single species (Anomma rubella) is referred to the Doryline by F. Smith (1868). I have not seen his description and figure of this insect, but his generic determinations of recent ants were often so erroneous that his competence to assign a fossil species to its proper genus may be doubted. The proportion of species in the other subfamilies is interesting because it is not unlike that obtaining at the present day. The number of indi

viduals belonging to each subfamily can be satisfactorily given only for the ants of the Baltic amber. Of the 2,158 specimens examined by Mayr and André, 764 were Camponotinæ, 1,310 Dolichoderinæ, 59 Myrmicinæ and 25 Ponerinæ. The great preponderance of Dolichoderinæ is due to two species, Bothriomyrmex gapperti (889 specimens) and Iridomyrmex geinitzi (248 specimens), which are represented by 1,137 specimens, or more than half of the total number. The species of Myrmicinæ and Ponerinæ are each represented by only a few individuals. From these facts Mayr concludes " that the Ponerinæ of the Tertiary exhibited the weakest development and have reached their full efflorescence in recent times." He advances a similar opinion in regard to the Myrmicinæ. Emery, however, has shown that this inference is erroneous, for the Ponerinæ-and the same is true of the Myrmicinæ are much less arboreal in their habits than the Dolichoderinæ and Camponotinæ, and would therefore be much less frequently entrapped in the liquid exudations of succiniferous trees. Then, too, the Ponerinæ probably formed small colonies as they do at the present time. I have found several undescribed Ponerinæ and Myrmicinæ both in the Baltic amber and in the shales of Florissant, showing that these groups must have been at least as highly diversified in the Miocene and lower Oligocene as the other two subfamilies.

Only in the amber species have the genera been at all satisfactorily established. Those described from other formations are very largely guesswork. This is especially true of such genera as Heer's Imhoffia, Attopsis and Poneropsis. Other species were placed by him and Scudder in the recent genera Lasius, Formica, Dolichoderus, Camponotus, Myrmica and Aphanogaster, but probably many of these allocations are erroneous. The only genera not represented in the amber, but occurring in the Tertiary strata, are Lonchomyrmex (Fig. 90) and Liometopum. We may divide the genera of the Baltic and Sicilian ambers into two groups, the extinct and recent, and the latter may be subdivided into those still represented by species in Europe (palearctic), which are nearly all common to the nearctic region as well (circumpolar), and those now confined to the tropics of the Old World (paleotropical). Grouping the genera thus, we have the table on page 167.

Of the 40 genera included in this table, 13 are extinct and 27, or more than two thirds, are still living. Of the latter, a little more than half (14) are still represented in Europe and a little less than half (13) in the Old World tropics. It will also be seen that the ratio (7:4) of exclusively paleotropical to palearctic genera in the Sicilian amber is nearly twice that of the Baltic amber (11:13), although very few specimens of the former have been examined. But it should