W. M. Wheeler.
Colonies of Ants (Lasius neoniger Emery) Infested with Laboulbenia formicarum Thaxter.
Psyche 17(3):83-86, 1910.

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PSYCHE
VOL. XVII. JUNE, 1910. No. 3.
COLONIES OF ANTS (LASIUS NEONIGER EMERY) IN- FESTED WITH LABOULBENIA FORMI-
CARUM THAXTER.
Harvard University.
It appears, from the exhaustive researches of Prof. Roland Thaxter, the leading authority on the Laboulbeniaceae, that only two species of these extraordinary ectoparasitic fungi are known to occur on ants. One of these species is Rickia wasmanni Cavara, found by Wasmann on Myrmica levinodis Nyl. at Linz on the Rhine; the other is Laboulbenia formicarum which Thaxter has taken at Cambridge, Mass. on Lasius niqer L. var. americanus Emery and Formica subpolita Mayr var. neogagates Emery. Both species are described and beautifully figured in the second part of Thaxter's "Contribution toward a Monograph of the Laboulbeni- aceae," Mem. Amer. Acad. Arts and Sci., Vol. XIII, No. VI, 1908, pp. 248 and 359, PI. XXXIV., Figs. 1-13 and Pl. LVIII, Figs. 14, 15.
For some time I have been looking for Laboulbeniaceae on the ants which I have collected myself or received from correspond- ents, but it was not till very recently that I happened on any speci- mens of these fungi. April 20-24, while collecting insects on the seashore at Ellisville, Mass., a small settlement about twelve miles south of Plymouth and six miles north of Bournedale, I came upon two localities about a mile apart, in which nearly all the colonies of Lasius niger, var. neoniger were infested with what Professor Thaxter has kindly identified for me as the second of the two species of Laboulbeniaceae mentioned above, namely Laboulbenia formi- carum. I first found a number of infested neoniger colonies a mile south of Ellisville in a small triangular area about a dozen yards in diameter and adjoining the beach. The soil of this area consists of a mixture of sand and humus and must be well within the reach of Psit-he 17:BJ-85 (1910). hupWpsych~-eincluborg/17/17-081 html



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84 Psyche [June
the salt spray during stormy weather. A few days later I discov- ered a much larger area, comprising a narrow strip about a quarter of a mile in length and forming the border of a salt meadow between Salt Pond and the beach at Ellisville. Here there are dozens of infested colonies which have a very definite and interest- ing distribution. On the beach itself, which consists of a deep layer of pure sand, there are colonies of Formica fusca var. argentata Wheeler, Myrmica scabrinodis Nyl. var. sabuleti Meinert, Tapinoma sessile Say and Lasius neoniger. The last is far and away the most abundant and its workers are of large size. None of the ants in this locality, including the neoniger, was found to be infested with Laboulbeniaceae. On the border of the salt meadow, however, immediately adjoining the beach, where the soil is moist, consist- ing of a mixture of rather sour, decomposing humus mixed with sand, and probably not infrequently wetted by the spray and oc- casionally even submerged at very high water, the only ant is L. neoniger, but its colonies are less populous than those on the beach, the workers are distinctly smaller and are practically all infested with the Laboulbenia. Passing over from this zone of infestation to the pasture land adjoining the salt meadow, the variety neoniger is replaced by L. niger L. var americanus Emery which is the form of the species commonly occurring in higher and dryer pastures and fields. None of the workers of this form, which lacks on the scapes and legs the erect hairs so conspicuous in the var. neoniger, was found to be infested with the fungus. It would seem, therefore, that while neoniger, unlike any of the other ants, is able to exist in a depauperate condition in the damp, sour soil at the edges of salt meadows, it does so only at the risk of becoming infested with Laboulbenia formicarum. Indeed, the infestation of the ants in this strip of littoral at Ellisville is often so excessive that they resemble hedgehogs, fairly bristling with tufts of the fungus. According to Thaxter, both Rickia wasmanni and Laboulbenia formicarum grow on all parts of their hosts, but this statement requires some qualification, at least in the case of the latter species. An examination of several hundred specimens of L. neoniger shows that the Laboulbenia grows most abundantly on the abdomen, mid- dle and hind femora and tibiae and posterior portions of the head. The thorax and coxse, as a rule, are entirely free from the fungus;



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19101 Wheeler -Ants Infested with Labonlbmia 85 the clypeus and gula are generally free, and this seems to be in- variably -the case with the mandibles, antennal funiculi, palpi, labium, maxillae and eyes. In a very few specimens I have seen one or two of the little plants on the antennal scapes, but, as a rule, these organs are perfectly clean.
Heavily infested workers were seen toiling at their excavations, constructing the craters of the nest and running about as nimbly as uninfested individuals, but the colonies, judging from their rather limited personnel and the reduced number and small size of the craters seemed to be decidedly less prosperous than those of the larger, uninfested form of the same variety on the sandy beach. I excavated a considerable number of the nests of the infested colo- nies but in only one instance did I find larvae, and I failed to find any queens, but as larvae were not seen in the uninfested colonies and as the old queens of all of our species of Lasius are very rarely seen in the nests, these negative observations have little significance.
It is strange that this should be the first time in my rather ex- tensive experience in collecting ants, that I have happened on a locality in which the colonies of a species are infested with Laboul- beniacese, and it is even more surprising that previous observers have found only two ant-infesting species of these fungi, which are represented by so many much larger and more remarkable forms on other insects. At first sight ants would seem to be particularly favorable hosts for such parasites since these insects are in the habit of huddling together in masses in warm subterranean gal- leries, where the fungi might be supposed to develop luxuriantly and transmit their spores from ant to ant with great facility.
Further consideration of the matter, however, leads to the con- clusion that other habits of the ants must, in all probability, tend to suppress or render impossible the development of the fungi, except under unusual conditions such as those in which I found the colo- nies of L. neoniger living at Ellisville. All ants devote a great deal of time and attention to cleaning their own integument and that of their nestmates. They are, indeed, forever combing and scraping the surfaces of their bodies with their tongues and strigils, so that fungi must find it difficult to gain a precarious foothold in their nests, to say nothing of an opportunity to proliferate. And even on



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