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CHAPTER 2 Identification and Classification An insect pest is a biological species (or population thereof), and entomologists should understand what this means in terms of pest management and control. Insect classification provides a framework within which all knowledge re- garding each species may be recorded. To the extent that the classification reflects genetic relationships, it permits useful generalizations and contains a high degree of predictability regarding pest species and their ultimate control. This predictability becomes more important as pest control becomes more complex. In order to retrieve reliable data from the classification, or to utilize its predictability, the classification must be accurate. Thus, correct identification of a pest species is the first step in scientific pest control. It provides a key to published information on the life history, behavior, and ecology of the insects, and to other data important in the development of control measures. When adequate published data regarding a particular pest species do not exist, the identification may furnish useful information through leads derived from published data on related species. Correct identification is also an essential element of plant-quarantine enforcement, exploration for foreign parasites and predators, search for insect resistance in crop varieties or animal breeds, and selective control procedures of all kinds. Initial taxonomic identification of pest species should be made by special- ists in taxonomy. Where sibling species, genetic strains, and biotypes involve pest species or their natural enemies, precise identification of these may be required in connection with control programs. In such cases, identifications should be made by laboratory or field biologists familiar with the physio- logical, behavioral, ecological, or genetic characteristics of the populations concerned.
10 INSECT-PEST MANAGEMENT AND CONTROL Although traditional methods of identification and data retrieval have served entomologists reasonably well, taxonomic methods must become mechanized and data retrieval systems must be vastly improved if the needs of entomologists are to be met satisfactorily in the future. Some suggestions for automated approaches to these problems are given later in this chapter. BIOLOGICAL-SPECIES CONCEPT AND MANAGEMENT To appreciate the problems confronting the systematist in classifying organisms and to anticipate certain problems in pest control, one must understand the nature of the biological species. Only a brief discussion can be included here; for fuller treatment the interested reader is referred to recent general works on evolution appearing in the bibliography at the end of this chapter. While the higher categories of the familiar biological classifi- cation (e.g., genera, families, and orders) can usually be recognized by characters observable in a single organism, the recognition of a species includes more than the tangible features of the specimen at hand. Modern systematics stresses the importance of the reproductive relationships among the individuals of a species rather than their anatomical similarities alone. This emphasis stems from the fact that the transmission of the genetic material through reproduction provides the only continuity between organisms in time and in evolution. The factors influencing the transmission of genetic material are therefore of interest in understanding the process of evolution and in scientific control of pests. Most of our knowledge concerning the genetics of populations has been deduced from the Mendelian laws of heredity. These laws apply only to sexually reproducing organisms or "Mendelian" populations. Each gene may exist in one of several states (or alleles). The relative frequency of a given allele in a Mendelian population may be computed, and predictions may be made about the frequency to be expected in subsequent generations under specified circumstances. One important deduction is that in the absence of certain modifying forces, the original frequencies of the genes in a large population can be expected to remain virtually unchanged in generation after generation. Changes in gene frequency in a large population may be expected if some of the genes in question mutate to another allele, some individuals possessing the gene are removed by natural selection before reproducing; or some of the individuals possessing the gene migrate from the population, or additional individuals migrate to the population. When a population is dis- tributed over an ecologically diverse region, the joint action of these modi- fying forces in each different situation leads to unique frequencies of many different genes within each area. Such adaptive complexes may or may not
IDENTIFICATION AND CLASSIFICATION 11 be distinguishable by anatomical differences. Furthermore, the exchange of genes between adjacent populations may be slightly to entirely reduced by physical or biological barriers. Populations thus isolated may be expected to become increasingly distinct and may or may not interbreed with adjacent populations if contact is re-established. Failure to interbreed with adjacent populations is the criterion by which species are defined in theory. A bio- logical species is formed by groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups or by the largest and most inclusive reproductive community of sexual and cross-fertilizing individuals which share in a common gene pool. The significance of these rudiments of the theory of population genetics may now be examined. First, it should be clear that the reproductive rela- tionships of a species can rarely be determined in practice. Other lines of evidence (similarity in anatomy, physiology, and behavior; and geographic continuity) must be used by the systematist to infer interbreeding unless actual field and laboratory information is available. Conclusions drawn from inferences alone may overlook populations similar or identical in characteristics but reproductively isolated even when in contact. Such popu- lations are called sibling species. Any program of pest control directed against a single species of organism should critically examine the evidence that the populations are conspecific. Similar economic problems may be created by two or more sibling species, and the techniques for control may be adequate for all. However, genetic differences that cannot be shared between the reproductively isolated populations may be important. For example, a specific inherited ability to resist insecticides will be restricted to those populations exchanging genes. Resistance in all other populations, even of the same species, must be developed independently. Control tech- niques applied to the same species throughout its distribution are actually being applied to different adaptive complexes with different susceptibilities to the controlling agents. Geographic differences in resistance to insecticides provide excellent examples. Pest conditions are commonly created by insects introduced from foreign countries, where they may or may not be of economic significance. Syste- matics plays an important role in determining the country of origin, so that native agents of biological control may be sought. The alien insect may be established from a single individual, and its success may be phenomenal. The colonization of new habitats, especially islands, has long been a favorite subject for systematic investigation. The results of these studies are of value in understanding the biology of an introduced pest. In view of the differences in local gene frequencies from place to place within the native range of a species, any small sample of individuals will probably not con- tain representatives of each of the alleles possessed by the species as a whole. Furthermore, the frequencies present in the sample are not likely
12 INSECT-PEST MANAGEMENT AND CONTROL to approximate the frequencies prevalent in the original local population. A sample of only one individual represents only a very small part of the genetic variation possessed by the species. Such small samples, however, often provide the initial colonizers of new habitats. Subsequent interbreeding within the small population may further reduce the genetic variation, since some alleles may be lost by chance (a phenomenon called genetic drift). The differences in ecology between the new and native environments drastically alter the selective advantages of the genes in the initial popula- tion, and new adaptive complexes are developed. The lack of parasites and predators and the presence of new host plants or animals, therefore, are only part of the explanation of the success of certain introduced insects. The circumstances of the introduction actually promote changes in gene frequency, and the colonizing populations may no longer resemble the native populations in many respects. The foregoing has been restricted to sexual and cross-fertilizing organisms. This is the most common type of reproduction among insects and is the type about which predictions can be made. However, parthenogenesis, or reproduction without fertilization, is not infrequent, but the theoretical consequences of this type of reproduction are little known. Hermaphro- ditism, or the possession of both sex organs by the same individual, is known only in the cottony-cushion scale, Icerya purchasi Maskell, and certain flies of the family Phoridae. The critical importance to agricultural entomology of studies of the systematics and evolution of pest species is demonstrated by species and variants of the weevil genus Hypera attacking alfalfa in the United States and Canada. A strain of the alfalfa weevil, Hypera postica Gyllenhal, was introduced into Utah from the Old World sometime prior to 1904. In the next 30 years, it gradually spread over most of western North America. This spread was accompanied by the evolution of populations in different parts of its range, (e.g., Lethbridge, Canada; Logan, Utah; and Tracy, California) to the now- different biological entities. Specifically, these entities differ in their response to the physical environment and in their behavior. For example, the Lethbridge weevils do not become active in the spring until the weather warms up to a higher level than that in Utah. This behavioral pattern protects the population from a sudden reversal in temperature and aids in their survival in a cold climate. This biological strain still belongs to the same species. A different strain of//, postica was introduced into the eastern United States sometime in the 1940's. It differs from the western form in a number of characteristics, e.g., cocoon construction, but still seems to be the same species. It has, in a rather short time, spread over much of the area east of the Mississippi River.
IDENTIFICATION AND CLASSIFICATION 13 A sweetclover-adapted strain (Melilotus) of the Egyptian alfalfa weevil, H. brunneipennis (Boheman), was introduced into the Yuma Valley of Arizona sometime in the 1930's. It was first thought to be the same as//. postica. However, it has widely different climatic adaptations from those of the more northern-adapted H. postica. For many years, H. brunneipennis remained associated with sweetclover in the Yuma Valley. Then, rather sud- denly, it became adapted to alfalfa. Populations increased, and it spread into California. It has become an important pest of alfalfa in southern California and recently moved into the central part of the state. Larvae of both H. postica and H. brunneipennis are parasitized by the ichneumon wasp, Bathyplectes curculionis (Thomson). It has recently been demonstrated on the basis of defense reactions of the weevils, i.e., encapsu- lation, that two strains of the parasite exist. The northern California strain of the parasite is only about 10% effective in attacking the southern H. brunneipennis, while the southern strain is about 85% effective. The northern strain is over 99% effective in attacking the northern H. postica, while the southern strain is about 90% effective. CLASSIFICATION FOR MANAGEMENT It has been widely held that one of the principal objectives of taxonomic classification is to provide a convenient filing system for recording facts about the vast array of living plants and animals that constitute the biological phase of man's environment. This viewpoint has been expressed most commonly with regard to the framework, or nomenclature, with .which classifications are constructed. This is an important function, but this same function might be accomplished more efficiently and effectively in other ways. Undoubtedly, greater effort would have been made to substitute a better data-filing system if this were, indeed, the principal objective of classification. The present system of biological nomenclature cannot now be easily replaced; until it is, the most immediate problem is to develop more-efficient means for re- trieval of data that have been recorded by means of a system discussed later in this chapter. Another objective of taxonomic classification is to attempt to express, through the nomenclatural system, degrees of relationship among the almost overwhelming variety of populations (species) of plants and animals existing throughout the world. This is accomplished by means of a hierarchy of taxonomic categories (genera, tribes, families, and orders) that are intended to express the degrees of relationship that taxonomic methods reveal. Taxonomists differ on such philosophical questions as whether taxonomic categories, including the species, actually exist in nature, and whether a
14 INSECT-PEST MANAGEMENT AND CONTROL phylogenetic system (a classification based on probable ancestry) using weighted characters or a phenetic system (a classification based on over-all similarity) using unweighted characters is superior. From the viewpoint of the applied biologist, these philosophical arguments are irrelevant. What is relevant is the extent to which classifications have built-in predictability. Until now, the best classifications arrived at by means of the traditional phylogenetic approach have exhibited a high degree of predictability, which can be and has been exploited in the solution of applied problems. If the time should come when phenetic classifications prove to have generally greater biological predictability, they may prove to be more useful in the applied field. The phenetic approach, having had few practitioners, has not been tried on a scale that would permit such a conclusion. The built-in predictability of "good" classifications has been used successfully many times in looking for the home of introduced pests in search of potential parasites. The method used has been to search in the center of distribution of the genus. However, if the classification is invalid and the generic assignment is incorrect, the results can lead to failure. For many years, the sugar-beet leafhopper, Circulifer tenellus Baker, vector of curly top virus, was incorrectly placed in the genus Eutettix. In 1918 the California Commission of Horticulture sent an explorer to Australia to search for the leafhopper and its natural enemies, but the insect was not found there. The United States Department of Agriculture surveyed the situation in Argentina and Uruguay in 1926-1928, and later in Mexico. Again, C. tenellus was not located, and no parasites were sent to the United States. As a result of effective systematics, the position of tenellus was clarified, and it was shown to be a representative of the Old World genus Circulifer. As a result, explorations in Spain and North Africa uncovered both C. tenellus and a large number of its parasites, which were liberated in the western United States. From 1877 to 1937 the red scale, Aonidiella aurantii (Maskell), was repeatedly misidentified, and its generic placement was particularly unsound and misleading. For a time this scale was placed in the genus Chrysomphalus, mostly a South American genus; therefore, a decision was made to search for enemies of red scale in South America in 1935. In 1937 more-precise taxo- nomic studies correctly placed red scale in the oriental genus Aonidiella, and the most promising natural enemies have been obtained from the Orient. IDENTIFICATION OF INSECT PESTS Taxonomic specialists in a position to make primary identifications of pest species or to refer inquiries to other specialists are employed by government
IDENTIFICATION AND CLASSIFICATION 15 agencies such as the United States Department of Agriculture (Insect Identi- fication and Parasite Introduction Research Branch, Entomology Research Division, Beltsville, Maryland, and Washington, D. C.), Canada Department of Agriculture (Taxonomy Section, Entomology Research Institute, Ottawa, Ontario), and Commonwealth Institute of Entomology, London, England; by many state departments of agriculture; and by many universities and museums. A list of taxonomists and the groups of organisms with which they work is available. (See the bibliography at the end of this chapter.) When the pest has been correctly identified, if it was previously known as a pest, the name will provide a key to published data with respect to its control, not only under its currently used name but also under any others (synonyms) applied to it in the past. If the species was not previously known to be a pest, or if adequate control measures have not been developed, the correct name (and its synonyms, if any) will lead to published information on the insect's life history, behavior, and ecologyâimportant in the development of suitable control procedures. However, correct identification of a pest should not be confused with determining the correct name of a pest. Rules governing the naming of animals and the methods for selecting the correct name, if more than one name has been applied to a species, are contained in the International Code of Zoological Nomenclature, published by the Inter- national Trust for Zoological Nomenclature (see the bibliography). Also, the International Trust has published official lists of generic and specific names that cannot be changed on purely nomenclatural grounds (see the bibliog- raphy). These lists include many names of economically important species, e.g. Cimex, Musca, Blatta, Nabis, Triatoma, Pulex, Oestrus, Gasterophilus, Hypoderma, and Locusta. However, in addition to scientific names, most pests have common names. A number of useful lists of common and scientific names of insect pests have been published in the United States, Great Britain, Canada, Australia, and Europe (see the bibliography). A useful guide to published information on insect pests and their control is the Review of Applied Entomology, a periodical of worldwide scope, published in London since 1913, which consists of two series, one providing abstracts of papers relating to agricultural entomology, the other, those relating to medical and veterinary entomology. If the pest is well known, information concerning it will probably be found in such a comprehensive work as Handbuch der Pflanzenkrankheiten. For North America, the Index to the Literature of American Economic Entomology provides a key to much of the published information about pests from 1917 to 1962, and references to important literature on the subject may be found in the United States Department of Agriculture Yearbook for 1952. Also, there are many books that discuss pest species. (See the bibliography for some of the most recent ones.)
16 INSECT-PEST MANAGEMENT AND CONTROL An important guide to published information on the life history, behavior, and other activities of insects is the classified index in the introduction to the Insecta section of the Zoological Record, published annually in London, England. Abstracts of much recent literature on insect biology, grouped by orders, may be found in Biological Abstracts, which also publishes B.A.S.I.C. and BioResearch Titles, which provide leads to articles through their titles. Extensive worldwide bibliographies on insects and their activities are available in review articles in Annual Reviews, Inc., published by the Entomological Society of America (1956 to date). Also, regional and world catalogs are avail- able for many insect groups, and these are useful in determining synonymy and, in some cases, in providing references to papers on biology. Unfortunately, few of them are current. There are numerous examples of the importance of correct identification to pest-control programs. One of the best known involves the epidemiology of malaria in Europe. Prior to 1930, the name Anopheles maculipennis Meigen was applied to superficially similar mosquitoes occurring widely over the continent, and these mosquitoes were believed to transmit the organism causing malaria. Control measures were directed against this "species" throughout much of its range. However, careful taxonomic studies eventually showed that the European "maculipennis" consisted of a complex of closely related sibling species with different geographical ranges, habitat preferences, and breeding habits. The discovery that not all of these species transmitted the malaria organism explained the anomaly previously observed, that malaria occurred discontinuously within the distribution of what had been considered a single "species." This information made it possible for the first time to direct control measures precisely where they would be most effective. A somewhat similar situation developed in North America with respect to screw-worm flies. For years, the name Cochliomyia macellaria (Fabricius) was applied to flies that laid their eggs in wounds and open sores in man and other animals, domestic and wild, as well as to flies that oviposited in carcasses of dead animals. Control measures involving trapping and burning carcasses failed to reduce the incidence of myiasis caused by flies ovipositing in wounds. Again, taxonomic studies revealed that two species were involved: C. macel- laria (Fabricius-), which bred in carcasses, and C. hominivorax (Coquerel), the myiasis-producing screw-worm. Trapping and burning of carcasses was aban- doned, and suppressive measures were aimed at the real culprit, ultimately resulting in control by spectacular sterile-male procedures described in Chapter 15. With reference to the significance of taxonomy in assessing the vector importance of arthropods in the epidemiology of arthropod-borne agents of diseases afflicting vertebrates, many examples could be cited where failure to
IDENTIFICATION AND CLASSIFICATION 17 differentiate closely related species of arthropods has resulted in misleading concepts as to vector roles. For example, early workers for a time confused the African tick Ornithodoros moubata (Murray) with O. savignyi (Audouin); these two species occupy different ecological niches, often in neighboring sites. At least some populations of the former are very important vectors of organisms causing relapsing fever in man, but there is now considerable doubt that O. savignyi transmits organisms that produce the fever. A more recent example of the need for meticulous taxonomic studies to support research on disease relationships of ticks has been cited, wherein the virus of Quaranfil fever in Egypt is associated with the tick Argas arboreus Kaiser, Hoogstraal, and Kohls, a species that would until recently have been identified as the closely related A. persicus (Oken). Hosts and distribution of these species are widely at variance. Although other examples might be cited to illustrate the importance of correct identification in programs involving chemical or physical control, the problem is particularly critical in relation to biological control. For example, the mealybug now known as Pseudococcus kenyae LePelley appeared in severe infestations in Kenya in 1923. It was first misidentified as P. citri, and, in 1925, unsuccessful attempts were made to introduce its parasites from Italy to Kenya. The pest was later thought to be P. lilacinus Cockerell, and it was referred to by this name until 1934. Enemies of P. lilacinus and other mealybugs were obtained from Java, the Philippines, Hawaii, and California, and all failed. Finally, the mealybug was correctly recognized as an undescribed species from Uganda, and parasites were obtained from that area; these parasites very quickly and completely suppressed the pest. SYSTEMATICS AND INFORMATION RETRIEVAL Stepwise, the general sequence of events that provides access to published reports of a pest is as follows: (1) the preliminary identification to a taxonomic level that will permit the specimen to be sent to the appropriate specialist, (2) the specific identification by a specialist in the taxa concerned, (3) the search for bibliographic citations that may contain information on the species, and (4) the finding of pertinent information contained in each published article. Part or all of each step must then be performed by trained personnel. The time consumed and the competency of the persons involved are important limitations on the speed and relevancy of the information supplied to a pest-control program. Under ideal circumstances, how can this procedure be accelerated and improved? It is convenient to discuss this question with regard to systematics and then with regard to information retrieval.
18 INSECT-PEST MANAGEMENT AND CONTROL An automated procedure in systematics should be expected to: (1) deter- mine the characteristics of a specimen, (2) place the characteristics in the computer memory, (3) create a classification of the specimens, (4) create a logical scheme or key to identify a new specimen as one of those previously processed or as a new taxonomic unit, (5) revise the classification and key for each new taxonomic unit, and (6) supply on request any desired infor- mation about the characteristics and classification of the taxa included. Steps 2 through 6 are already well within the capacities of modern electronic computers. The number of taxa that may be accommodated, however, is still restricted by the size of the computer memory. Techniques are being developed by systematists and others to automate the classification and identification of an organism once the characteristics are known. To take full advantage of the computer, certain changes may be expected in the structure of classification, the formation of the "key," and the definition and designation of species. A uninominal nomenclature and a numericlature, for example, have been proposed to increase stability of scientific names and to facilitate automation. Step 1, the determination of characteristics, remains the major obstacle to a fully automated procedure. Characters can, of course, be observed and entered into the computer by a systematist. An automated key with televised illustrations of the alternative choices could be constructed for identification by persons with less training. Similar solutions will have to suffice until the characters can be taken directly from the specimen by a machine. Devices exist for scanning certain parts of the body or microscopic preparations and storing this information in a computer. However, appraisal of the usual morphological features may not be the most desirable choice of character- istics. Ideally, an analysis of the genetic material or "code," or certain biochemical products of the code might be desirable. Such a procedure is under study in bacterial classification, with the prospect of an automated biochemical analysis of a sample and the subsequent automatic identification. Similar procedures might be applied to insects by utilizing the combined efforts of biochemists, physiologists, and systematists. Considering the enor- mous difficulties now involved in the identification of compounds in careful physiological investigations, some time may be required before comparative analyses can be made routinely. The effects of age, diet, sex, physiological condition, and geographic distribution will have to be evaluated. Cuticular waxes, for example, might prove unique for a species, as they have for some plants. Patterns automatically derived from gas chromatography or mass spectrometry might serve the purpose of the systematist equally well without necessarily identifying the responsible compounds. Progress in the area of an automated systematic procedure is retarded not merely by a lack of suitable instruments but also by our imperfect knowledge
IDENTIFICATION AND CLASSIFICATION 19 of much of the world's fauna. The latter problem is especially acute in dealing with insects encountered in pest control. Introductions may be expected from virtually any part of the globe. A fully automated procedure functioning now would only be able to decide that a specimen was new, but further informa- tion as to the country of origin, and habits, for example, might not be available. Turning now to information retrieval, the goal of an automated procedure might be to ask, "What is known about XI" and to receive copies or a visual display of the desired information in the desired language. To achieve this end, the actual text and graphic material would have to be placed in the com- puter; the information in the articles would have to be cross-indexed and, if necessary, translated; and portions of the articles would have to be reproduced on demand. Again, the initial step of placing the information in the computer is the major obstacle. Text and graphic materials are already commonly con- verted into digital-computer storage and subsequently retrieved in the form of automated commercial printing processes and television. If all present and future publications relevant to pest control were so treated, part of the task would be accomplished. Critical reviews and monographic studies would be especially helpful. Past publications may prove to be only a small part of the total. Selections from these would have to be entered by hand key-punching until an automated reader is developed. Once the text is stored in a com- puter, it is available for various cross-indexing systems and for translations. Solutions to the general problems of information retrieval, indexing, and translation are being sought by many groups. Fortunately, some of the problems facing other areas of human knowledge were solved long ago by systematists. The hierarchical structure, the elimination of synonyms and homonyms, the international terminology, and the mutually exclusive taxo- nomic units are among the attributes of biological classification that greatly facilitate automation. Because of the unitized format of most taxonomic publications, strictly taxonomic information such as descriptions of new species, distribution records, and host preferences could easily be retrieved from a computer. The use of common names adds some complication, but uniform usage as proposed by the Entomological Society of America has minimized this source of confusion in recent publications in the United States. Uniqueness of most of the chemical and commercial names of in- secticides simplifies automatic retrieval of information. Entomologists must now maintain a file of simple or edge-punched cards with an elementary cross-indexing system. Additions to the file are usually made by the chance finding of an article or by routinely searching periodicals containing cross-indexing citationsâsuch as Zoological Record, Biological Abstracts, and allied publications; Bibliography of Agriculture and Pesticides Documentation Bulletin; and Guide to the Literature of the Zoological
20 INSECT-PEST MANAGEMENT AND CONTROL Sciences. These are necessary aids to information retrieval, but the present procedure suffers a number of disadvantages: (1) not all articles are included; (2) commonly only information in the bibliographic citation is cross-indexed, leaving the specific units of information in the article not indexed; (3) actual text and graphic material must be sought in the original publication; (4) only the simplest systems of cross-indexing can be handled in the individual file; and (5) much effort is duplicated by investigators with similar interests. Catalogs of insect groups are of great benefit to all entomologists in informa- tion retrieval (see the bibliography). The initial preparation of a catalog and the updating of its contents are best performed by automatic devices. An automated system, then, is probably both more efficient and less expensive. Instantaneous identification and information retrieval are not likely to materialize within the next few decades. Pioneering steps must be taken toward solutions to these problems in pest control, not only to take advantage of the technology already available, but to be prepared to utilize the facilities of the future. BIBLIOGRAPHY Anderson, R. F. 1960. Forest and shade tree entomology. John Wiley & Sons, Inc., New York. 428 pp. Beaulieu, Andre'-A. et al. 1947. Liste officielle des noms franjais des insects d'importance economique au Canada. 1st ed. Quebec, Ministe're de 1'Agriculture. 65 pp. Blackwelder, R. E., and R. M. Blackwelder. 1961. Directory of zoological taxonomists of the world. Southern Illinois Univ. Press, Carbondale. 404 pp. Blickenstaff, C. C., Chairman, Committee on common names of insects, Entomological Society of America. 1965. Common names of insects approved by the Entomological Society of America. Bull. Entomol. Soc. Amer. 11:287-320. British Association of Applied Biologists. 1947, 1952. Common names of British insects and other pests. Parts I, II. Carter, W. 1962. Insects in relation to plant disease. Interscience Publishers, Inc., New York. 705 pp. Cotton, R. T. 1963. Pests of stored grain and grain products. 4th ed. Burgess Publishing Co., Minneapolis, Minnesota. 318 pp. Craighead, F. C. 1950. Insect enemies of eastern forests. U.S. Dep. Agr. Misc. Publ. 657. 697 pp. Davidson, R. H., and L. M. Peairs. 1966. Insect pests of farm, garden and orchard. 6th ed. John Wiley & Sons, Inc., New York. 675 pp. Dobzhansky, Th. 1950. Mendelian populations and their evolution. Amer. Natur., 84:401-418. Dodge, B. O., and H. W. Rickett. 1943. Diseases and pests of ornamental plants. J. Cattel Press, Lancaster, Pa. 638 pp. Ehrlich, P. R. 1964. Some axioms of taxonomy. Syst. Zool. 13:109-123. Ehrlich, P. R., and R. W. Holm. 1963. The process of evolution. McGraw-Hill Book Co., Inc., New York. 347 pp.
IDENTIFICATION AND CLASSIFICATION 21 Gay, F. J. 1955. Common names of insects and allied forms occurring in Australia. Commonwealth Sci. Ind. Res. Organ. Australia, Melbourne. Bull. 274, 32 pp. Hall, D. G. 1952. How to get further information on insects. In Insects. U.S. Dep. Agr. Yearb. 1952, pp. 737-743. Herms, W. B., and M. T. James. 1961. Medical entomology. 5th ed. Macmillan Co., New York. 616pp. Hey wood, V. H., and J. McNeill, Editors. 1964. Phenetic and phylogenetic classification. Syst. Ass. Publ. 6. 164pp. Hickin, N. E. 1964. Household insect pests. Hutchinson & Co., London. 172 pp. Hull, D. L. 1966. Phylogenetic numericlature. Syst. Zool. 15(l): 14-17. International Commission on Zoological Nomenclature. 1958a. Official list of generic names in zoology. Part 1, Names 1-1274. International Trust for Zoological Nomenclature, London. 200 pp. International Commission on Zoological Nomenclature. 19586. Official list of specific names in zoology. Part 1, Names 1-1525. International Trust for Zoological Nomen- clature, London. 206 pp. International Commission on Zoological Nomenclature. 1961. International code of zoological nomenclature. International Trust for Zoological Nomenclature, London. 176 pp. Keen, F. P. 1952. Insect enemies of western forests. U.S. Dep. Agr. Misc. Publ. 273. 280pp. Leone, C. A., Editor. 1964. Taxonomic biochemistry and serology. The Ronald Press Co., New York. Little, F. J., Jr. 1964. The need for a uniform system of biological numericlature. Syst. Zool. 13:191-194. Mayr, E. 1942. Systematics and the origin of species. Columbia Univ. Press, New York. 334 pp. Mayr, E. 1963. Animal species and evolution. Harvard Univ. Press, Cambridge, Massachusetts. 797 pp. Mayr, E. 1965. Numerical phenetics and taxonomic theory. Syst. Zool. 14:73-97. Mayr, E., E. G. Linsley, and R. L. Usinger. 1953. Methods and principles of systematic zoology. McGraw-Hill Book Co., Inc., New York. 328 pp. Mendelsohn, M. L., W. A. Kolman, and R. C. Bostrom. 1964. Initial approaches to the computer analysis of cytophotometric fields. Ann. N. Y. Acad. Sci. 115 (art. 2): 998- 1009. Metcalf, C. L., and W. P. Flint. 1962. Destructive and useful insects: Their habits and control. 4th ed. Revised by R. L. Metcalf. McGraw-Hill Book Co., Inc., New York. 1087 pp. Michelbacher, A. E. 1940. The value of accurate classification of insects as illustrated by the confusion of two closely related species otHypera. Proc. 6th Pac. Sci. Congr. IV: 403-405. Michener, C. D. 1963. Some future developments in taxonomy. Syst. Zool. 12:151-172. Michener, C. D. 1964. The possible use of uninominal nomenclature to increase the stability of names in biology. Syst. Zool. 13:182-190. Muesebeck, C. F. W., et al. 1951. Hymenoptera of America north of Mexico, synoptic catalog. U.S. Dep. Agr. Monogr. 2. 1420 pp. Parrish, D. W., J. D. de Coursey, and J. M. Geary. 1966. Present and future concepts in the gathering of entomological information. Bull. Entomol. Soc. Amer. 12:128-136. Rivas, L. R. 1965. A proposed code system for storage and retrieval of information in systematic zoology. Syst. Zool. 14:131-132.
22 INSECT-PEST MANAGEMENT AND CONTROL Ross, H. H. 1965. A textbook of entomology. 3rd ed. John Wiley & Sons, Inc., New York. 539pp. Savory, T. 1962. Naming the living world. John Wiley & Sons, Inc., New York. 128 pp. Schlinger, E. I., and R. L. Doutt. 1964. Systematics in relation to biological control, p. 247-280. In DeBach, P., and Schlinger, E. I., Editors. Biological control of insect pests and weeds. Chapman and Hall, London. Schmidt, G. 1939-1940. Gebrauchliche Namen von Schadinsekten in Verschiedenen LUndern (Popular names of insect pests in various countries). Entomologische Beihefte 6:1-160; 7:161-354. Simpson, G. G. 1961. Principles of animal taxonomy. Columbia Univ. Press, New York. 247 pp. Simpson, G. G., A. Roe, and R. C. Lewontin. 1960. Quantitative zoology. Rev. ed. Harcourt, Brace & World, Inc., New York. 440 pp. Smith, R. C., and R. H. Painter. 1967. Guide to the literature of the zoological sciences. 6th ed. Burgess Publishing Co., Minneapolis, Minnesota. Sokal, R. R. 1966. Efficiency in taxonomy. Taxonomy 15(l): 1-21. Sokal, R. R., and P. H. A. Sneath. 1963. Principles of numerical taxonomy. W. H. Freeman and Co., San Francisco, California. 359 pp. Stone, A., C. W. Sabrosky, W. W. Wirth, R. H. Foote, and J. R. Coulson. 1965. A catalog of the Diptera of America north of Mexico. U.S. Dep. Agr. Handb. 277. 1696 pp. United States Department of Agriculture. 1952. Insects. U.S. Dep. Agr. Yearb. 1952. 780 pp.
