Mermis Parasitism in Pachycondyla striata.
Psyche 35(4):199-200, 1928.
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19281 Mermis Parasitism in Pachycondyla striata 199 MERMIS PARASITISM IN PACI2YCONDYLA STRIATA. BY T. D. STRELNIKOV
In my collection of ants from Alto Parana (Paraguay) I en- countered a large specimen of Pachycondgla striata F. Sm. which was infected with a nematode worm (Mermis). In a recent paper by Professor W. M. Wheeler1 the whole problem of Mermis Fig. 1. a, Pachycondyla striata; normal; b. Pachycondyla striala; Mermithized; c, head of normal worker from above; d, head of Mermithergate. parasitism and intercastes among ants is reviewed. He has given an account of all cases of mermithism, including several new cases among certain Neotropical Formicidse. Professor Wheeler gives also an interpretation and a discussion of the whole problem of mermithized ants and a list of the relevant literature. The Pachycondyla striata from Paraguay, which I have Wheeler, W. M. Mermis Parasitism and Intercastes among Ants. Journ. Exper. Zool. Vol. 50, No. 2, 1928.
200 Psyche [December
studied in Professor Wheeler's laboratory at the Bussey Institu- tion, represents a new case of mermithization, similar to that of Pachycondyla fuscoatra, described by Emery. Pachycondy7a striata was found in small colonies under dead leaves. It stings severely and when disturbed can bury itself quickly into the ground. I encountered the parasitized specimen of Pachycondyla striata running along a trail in the forest in the neighborhood of Puert'o Bertoni, where the famous naturalist Dr. M. S. Bertoni lived. The movements of the ant were slow. The differences presented by the morphology of the pa- rasitized Pachgcondyla striata in comparison with an unparasitized specimen may be seen from the accompanying figures.2 The gaster of the mermithergate is very voluminous and swollen. In the normal ant t'he abdominal segment's are fitted into one another so as to allow the abdomen to dilat'e as a whole. But in the parasitized individual some of the segments are more or less separated from one another, so that the abdomen is increased in length from 6.5 mm. in a normal to 8.5 mm. in the mermithergate individual and from 2.25 to 3 mm. in diameter. The petiole of the parasitized ant is narrower andlower, than in normal workers. Some modifications in the thorax were also observed. The pronoturn of the mermithergate is shorter and the epinotum narrower than in normal P. striata.
The greatest difference is discernible in the head, which in t'he parasitized specimen is conspicuously smaller and less robust, i. e. narrower and shorter, and of a peculiar narrow, more rec- tangular shape behind the eyes. There are no traces of ocelli. The mandibles of the infected specimen are narrower and smaller, the antenna1 scapes decidedly shorter and a little thinner. The funiculus is also slightly shorter.
The surface of the body is smoother and more shining than in normal P. striata workers, owing to the fewer hairs on all parts of the body.
The color of the hairs is also different. In the parasit'ized specimen they are more grayish, but in normal P. siriata they are golden-yellow.
In the intersexual form of P. striata we have parasitic cas- t,ration and mingling of the normal secondary sexual characters. 2Made by camera lucida.
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