Methods of Marking Insects, with Especial Reference to Orthoptera (Sens. Lat.)2

Abstract

Radioactive and nonradioactive methods used in the past for marking insects, and their applicability to or-thopterous insects (sens, lat.), are evaluated on the basis of experimentation, prior field and laboratory experience, and critical analysis of pertinent literature. Radioactive methods based on external application of the isotope are found unsatisfactory for use on Orthoptera; but internal application by ingestion, by surgical insertion, and especially by injection, are suitable for this group of insects, though the ingestion method is subject to several limitations. The nonradioactive methods, grouped into 13 broad categories, are virtually all unsatisfactory for Orthoptera. Fluorescent materials (for nocturnal species) and various kinds of paints indicate some promise, but their applications are limited. One method, the amputation of tegmina, is useful, especially in combination with the new "notch technique." This latter consists of the removal , with fine iris scissors, of V-shaped portions of exoskeleton from the fore, hind, and lateral margins of the pronotum. Various assortments of these notches, in combination with half or full amputation of tegmina, yield a large number of distinctive marks which are readily applied and interpreted in the field, easily supplemented with paint, and reasonably persistent through at least the later life stages; yet they do no apparent harm to the tagged insects. During the course of a population study of certain Orthoptera of an oldfield community, 5 it became necessary to mark individual Orthoptera. Several techniques were tried and discarded as unsatisfactory until a new method, the "Notch Technique," was developed. Because of the opportunities notching presents for behavioral and population research on Orthoptera, as well as certain other insectan groups composed of heavily sclerotized comparatively large individuals, a description of the technique seemed appropriate. A review of the literature dealing with insect marking disclosed that this method is new, and that there are certain other methods of tagging which might also be of some utility. These findings suggested that evaluation of each method for use in tagging Orthoptera was appropriate. The following report presents the results of this evaluation. Its triple objective is the discussion of previously utilized methods of marking insects, analysis of their application with respect to Orthoptera, and description of the "Notch Technique." THE USES OF MARKING Insect marking may be utilized for numerous purposes , including: (1) following the movements and activities of individual animals, which include flight, locomotion on the ground, movements within the soil or on plants, habitat selection, and feeding and sexual activities; (2) detecting the number of ecdyses; (3) studying the dispersal, flight range, migrations, and other gross movements of individuals and populations from environment to environment; and (4) determining population density, differentiation of age groups, sex ratio, length of life, and mortality. Number 1 requires that the mark be distinctive from that given all other individuals of the population; i.e., a code must be used. The other described purposes (2 through 4) may or may not necessitate use of a