Some ant-aphid associations in Manitoba with observations on interactions between Formica oreas comptula wheeler and aphids at Birds Hill Park, Manitoba

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Madder, Mary Catherine Anne
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...A survey of Manitoba ant-aphid associations was conducted by collecting and identifying samples of ants and aphids found together on aphid host plants. Qualitative and quantitative monitoring of the interactions of Formica oreas comptula with Symydobius americanus, Chaitophorus saliciniger and Pterocomma smithiae was carried out during 1977 at Birds Hill Park. Data were analyzed by stepwise multiple linear regression analyses. Twenty-seven species (seven genera) of ants tending 62 species (28 genera) of aphids on 39 host plants were collected in Manitoba during 1976 and 1977. Formica species were the dominant aphid-attendants and Aphis species wee the most frequently attended aphids. 9.7% of the associations contained two different ant species or genera together; usually one was the true aphid-attendant and the other a scavenger species. F. oreas comptula workers were always present at the aphid colonies, at least until mid-June; however, the individual aphid-attendants changed throughout the day and night. Demand for aphid honeydew diminished by mid-June, possibly due to departure of males and queens from the ant nest. Aphid excretory behavior changed when this decrease in ant attendance occurred, and other ant species were then frequently observed at or near the aphid colonies. Marking experiments suggested that age polyethism and task fidelity exist in F. oreas comptula, and that some ants which were present at the aphid colonies in the spring may have been foragers surviving from the previous summer... F. oreas comptula were aggressive toward moving insects near the aphid colonies they were tending; they did not respond to syrphid larvae feeding on the aphids. Aphid parasitism and predation were not prevented by the ants' presence, and were greatest in colonies of C. saliciniger.