Section 34
Chapter 33,018

Protozoan parasites of the Orthoptera, with special reference to those of Ohio III Protozoan parasites in relation to the host and to host ecology

Semans, Frank Merrick

Ohio Jour Sci 41(6): 457-464


Accession: 033017464

99 spp. of Orthoptera were examined, with 34% infection; 1287 individual specimens, with 19% infection. It is indicated that the protozoan parasites of the Orthoptera are host-specific for families and, to some extent, for subfamilies. Protozoan parasites were taken from species of all of the major subdivisions of the Orthoptera studied, except the Phasmidae, Tettigoniidae, and Oecanthinae (subfamily of Gryllidae). The distinctive appearance of the gut contents and the gut pH of the latter two were correlated with the absence of parasites in these groups. The number of Phasmidae was too small to justify making a statement concerning the absence of parasites. 22 (or 24?) new hosts were recognized, and 12 (or 10?) hosts already studied were assigned new parasites. (The exact number is doubtful because of a few inaccurate host determinations made in the past.) The infection* by cephaline Gregarinida of nymph Orthoptera was approx. 1/2 as frequent as that of adults, but the degree of infection by flagellates (1 sp.) was about the same in nymphs and adults. Female insects were infected by gregarines slightly more often than [male][male] not nearly so often by flagellates. Ciliates (1 sp.) were taken from 1 host only. No amoebae were observed. The predominating seat of gregarine infection was the extreme ant. end of the mid-intestine at the base of the enteric ceca. However, other parts of the mid-intestine, including the enteric ceca, were sometimes infected. Flagellates and ciliates were taken from the hind-intestine, particularly the colic region. The average pH of the ant. end of the mid-intestine of Tettigoniidae and Oecanthus spp. of the Gryllidae (where there is probably no parasitism) was lower than that of specimens of 2 other orthopteran subdivisions which are known to be freely parasitized. There was a tendency for the gut pH to correlate with that of the soil of the locality in which the insect lived. In general, the greatest degree of parasitism was in well-fed Orthoptera which were terrestrial, scavengers, and cannibalistic.

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