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A Contribution to the Study of the Ecology of Corixidae (Hemipt.)

T. T. Macan
Journal of Animal Ecology
Vol. 23, No. 1 (May, 1954), pp. 115-141
DOI: 10.2307/1663
Stable URL: http://www.jstor.org/stable/1663
Page Count: 27
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A Contribution to the Study of the Ecology of Corixidae (Hemipt.)
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Abstract

1. One hundred and seventeen miscellaneous collections of corixids made by the author are analysed, the principle being to arrange the collecting places into groups according to the predominant species and then look for features common to each group. Frequent comparisons with the findings of other workers are made. The following arrangement emerges: Group I. Corixa lacustris, C. falleni and sometimes C. concinna; rivers, ditches, lakes and one pond. C. lacustris occurs at almost every station; C. falleni has a more restricted habitat being absent from the more exposed stations and from lime-deficient waters; C. concinna, a rare species, is possibly associated with a salinity higher than is usual in inland waters. C. distincta and C. fossarum replace C. lacustris in sheltered places where organic matter accumulates. Group II. C. sahlbergi; stagnant usually small places with much decomposing vegetable matter. Other species are few. Group III. C. praeusta; rivers, large ponds, and small lakes that are highly productive, somewhat polluted or enriched by dead leaves. All the group I species occur frequently. C. praeusta, known to be a ready flier, is predominant in two recently filled ponds. Group IV. C. scotti, C. castanea, C. semistriata, C. venusta, C. germari, C. wollastoni, C. nigrolineata; mountain, moorland, heath, bog, or in one instance fen pools, ponds and streams. C. scotti and C. castanea are the two species most typical of lime-deficient conditions. At high altitudes they give place to C. wollastoni and C. nigrolineata. C. venusta is sometimes found in ponds where it is difficult to see why C. scotti is not the main species and it occurs in small numbers in high pools. It is, however, found most often in running water, and there are several records of it in quarry pools in which the bottom is covered with the debris of quarrying. C. semistriata sometimes occurs with C. scotti and C. castanea but more commonly in small pools in fen peat. C. germari and Glaenocorisa propinqua seem to be typical of large shallow places with a uniform depth and inhabit the deeper water. Group V. Corixa nigrolineata, C. punctata, C. lateralis; productive ponds. In a typical pond with plenty of vegetation there will be at least four or five species with C. punctata among the commonest. C. lateralis is favoured by intense animal fouling and is found also in ponds near the sea. The habitat of C. nigrolineata is less easy to define; many of the places are small and shallow. Apart from two specimens in group III, C. limitata was found only in group V. 2. Methods of calculating degree of association between species are discussed. 3. Information is extracted from various published papers and some MS. records, and the coefficients of association between the species of corixid from 400 places are calculated by Cole's method. 4. An unexpectedly high number of positive associations are found and reasons for this are discussed. 5. The species can be arranged, according to their associates, in three groups which coincide well with those of the previous analysis. These groups are: pools and ponds on base-poor soil (group IV), productive ponds (groups II and V), and lakes and rivers (groups I and III). The first, if two species be excluded, has few outside associations, the second and third have many common associations. 6. A diagrammatic representation of the relationships of the eleven most common species, based on the coefficients of association, is found to agree fairly well with a figure based on subjective analysis. 7. On the whole the results of the mathematical analysis tally well with subjective conclusions and are particularly useful in revealing relationships of rare species.

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