Identification

In principle the identification of insects is the same as that of any other animal. In practice it is more difficult, for two major reasons. First, the enormous number of species that occur means that often very minor differences in structure must be used to distinguish between forms, and second, the small size of most insects frequently means that the identifying characters are not easily seen. There are various methods for identifying organisms:

(1) the specimen may be sent to an expert, (2) it may be compared with the specimens in a labeled collection, (3) it may be compared with pictures or descriptions, or (4) it may be identified by use of a key. Pictorial keys, which can be valuable to both specialists and non-specialists, include not only printed material but also user-friendly computer-based interactive systems such as those developed by Bishop et al. (1989), Lawrence et al. (1993), and Weeks et al. (1999). Most often, however, only conventional written keys are available. A tentative identification from a key should be confirmed by comparing the specimen's characters with the diagnosis or description for the species.

There are different ways of arranging a key, though all involve the same general principle, namely, the stepwise elimination of characters until a name is reached. Keys may be devised so as to reflect the evolutionary relationships between the taxa identified. However, because character state differences between closely related taxa may be slight, the use of a phylogenetic key with "weak" or "difficult" couplets may make identification difficult. Thus, most keys are quite arbitrary, as they have as their only objective, ease of identification. In this arbitrary system the same taxon may key out at several points in the key, whereas in a phylogenetic key, the taxon would appear only once.

Typically, a key is in the form of a series of couplets (occasionally triplets may be included) of contrasting character states. For maximum usefulness, the couplets should present clear-cut alternatives for the characters under consideration. The simplest form of sequence within a key is one in which each couplet includes only a single character. The drawback of such monothetic keys is that they do not work for organisms in which a character does not follow the norm. The alternative is a polythetic key in which at least some couplets include several statements, each about a different character. Sneath and Sokal (1973) suggest three reasons for using polythetic keys: (1) one or more characters may not be observable (e.g., if the specimen is incomplete, damaged, or at the "wrong" life stage),

(2) some species may be exceptional for a particular character, and (3) the user of a key may err in deciding about a character. By having several characters in each couplet with which to work, a user can operate on a "majority vote" basis, that is, select the branch of the couplet that overall most closely describes the characters of the specimen. A disadvantage of such an arrangement is that a decision on which branch to select may not be clear-cut (especially if the specimen is exceptional in one of the characters listed). Further, the "rules" to be followed in a polythetic key must be carefully stated [i.e., do all characters in a couplet have equal value, or does one (the first) or more carry greater weight—and, if so, how much?].

A serious drawback to many keys is that in order not to become unwieldy they are constructed either specifically for identification of specimens in a particular geographic area or for identification of specimens to a higher taxonomic level only, typically to family. This is especially true of insect keys because of the great diversity of the insect fauna. In short, their use may be rather limited. The arrangement in this text is the provision of a polythetic key for identification of insects to the level of order, rarely the suborder. A list of keys for identification beyond the ordinal level is then provided under the description of each order (see Chapters 5-10). This list is by no means exhaustive, and it is anticipated 103

that instructors will direct students to useful keys for the geographic area or insect group of

interest. TAXONOMY

Beekeeping for Beginners

Beekeeping for Beginners

The information in this book is useful to anyone wanting to start beekeeping as a hobby or a business. It was written for beginners. Those who have never looked into beekeeping, may not understand the meaning of the terminology used by people in the industry. We have tried to overcome the problem by giving explanations. We want you to be able to use this book as a guide in to beekeeping.

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