The limnological relations of insects to certain aquatic flowering plants

TitleThe limnological relations of insects to certain aquatic flowering plants
Publication TypeJournal Article
Year of Publication1952
AuthorsMcGaha Y.J
JournalTransactions of the American Microscopical Society

1. Limnological relations of insects to 13 species and 1 variety of hydrophytes were investigated in 5 counties of the lower peninsula of Michigan. 2. Sixty-one species of insects were studied, of which 58 are either phytophagous or at least under certain conditions use tissues of hydrophytes as food. 3. These insects include 3 species of Homoptera, 16 species of Coleoptera, 20 species of Trichoptera, 7 species of Lepidoptera, 14 species of Diptera and 1 species of Hymenoptera. Certain unidentified Odonata, both Zygoptera and Anisoptera, insert eggs into plant tissue. 4. The total number of insects found associated with each plant is as follows: Sagittaria latifolia, 9; Sagittaria latifolia diversifolia, 10; Anacharis canadensis, 2; Vallisneria americana, 4; Zizania aquatica, 4; Ceratophyllum demersum, 0; Nymphaea odorata, 25; Nymphaea tuberosa, 15; Nuphar advena, 13; Nuphar variegatum, 24; Brasenia Schreberi, 2; Myriophyllum exalbescens, 7; Myriophyllum heterophyllum, 7; Utricularia vulgaris, 1. 5. These plants do not belong to closely related botanical groups. They may be placed into 3 ecological groups on the basis of their relations to water. Although there is some intergradation, each ecological group supports a characteristic insect assemblage. 6. The insects studied in this investigation show various degrees of restriction in their choice of food plants. Those living on submerged hydrophytes make use of a wide variety of plants, others which feed on floating or emergent vegetation may be restricted to one or a few species of plants. 7. These insects vary in their degree of aquatic adaptation from those equippped with gills and well suited to life in water to those with holopneustic respiration. 8. The phytophagous Trichoptera when kept under crowded conditions in aquaria often became predaceous or even cannibalistic. In the laboratory species usually considered as predatory consumed quantities of plant tissues. 9. Some phytophagous Trichoptera larvae feed during both day and night inflicting characteristic damage upon different plants. 10. Factors such as wave action, silting and certain kinds of pollution either prevent insects from living on plants or greatly reduce their populations. 11. Plants suffer considerable injury due to these insect infestations. Eggs and respiratory spines are inserted into plant tissues; juices sucked from leaves; part of leaves used for case-making; stems, roots and petioles gnawed upon or burrowed into and plants sometimes completely defoliated. 12. Fluctuations occur in insect populations on hydrophytes. They can usually be explained upon the basis of emergences and broods. 13. Several species are recorded from certain counties for the first time and a few are new records for Michigan. 14. These hydrophytes support a large, heterogeneous insect fauna of which some species are intimately, and in some instances obligatorily related to the plants. Others subsist on a wide variety of both animal and plant matter and no species of plant studied is essential for their well-being so long as an adequate food supply is available.