Systematics And Taxonomy

Toward the end of the 19th century the full force of Darwin's ideas on evolution and 99

the importance and usefulness of fossils began to make themselves felt in insect classification. Gone was the old idea that evolution was a single progressive series of events, and in its place came the appreciation that evolution was a process of branching. Thus, insect classification entered, at the beginning of the 20th century, the phylogenetic phase of its development, although Haeckel (1866)* had been the first to use a phylogenetic tree to indicate the relationships of the Insecta. Unfortunately his ideas on genealogy were incorrect. Most recent systems have been influenced to some degree by the work of an Austrian paleoentomologist, Handlirsch, who criticized earlier workers for their one-sided systems, in which a single character was used for separation of the major subdivisions. Another failure of the 19th century authors was, he claimed, their inability to distinguish between parallel and convergent evolution of similar features. Finally, he pointed out that almost no one had taken into account fossil evidence. Handlirsch's first scheme, produced in 1903, was, at the time, regarded as revolutionary. He raised the Collembola, Campodeoidea (= Diplura), and Thysanura each to the level of class. (Prior to this the Diplura had been considered usually as a suborder of the Thysanura.) He also raised the Pterygogenea of Brauer to the level of class and arranged the 28 orders of winged insects in 11 subclasses. His second scheme, published in 1908, was identical with the first except for some slight changes in the names of orders. In 1925 Handlirsch published his modified views on insect classification. In this scheme he reintroduced Brauer's two subclasses, Apterygogenea and Pterygogenea. In the former group he placed the orders Thysanura, Collembola, Diplura, and the recently discovered Protura. In the Pterygogenea he listed 29 orders (including the Zoraptera, first described in 1913) arranged in 11 superorders (his former subclasses). The most significant point in Handlirsch's work was his recognition of the heterogeneous nature of the Orthoptera, the contents of which he split into orders and regrouped with other orders in two superorders, Orthoptera (containing the orders Saltatoria, Phasmida, Dermaptera, Diploglossata, and Thysanoptera) and Blattaeformia (containing the Blattariae, Mantodea, Isoptera, Zoraptera, Corrodentia, Mallophaga, and Siphunculata). He did not appreciate, however, the orthopteroid nature of the Plecoptera and placed the group in a superorder of its own. Handlirsch was also in error in regarding the Corrodentia, Mallophaga, and Siphunculata as orthopteroid groups. They are undoubtedly more closely related to the Hemiptera. Handlirsch's arrangement was strongly criticized by Borner (1904), who said that it did not express the true phylogenetic relationships of the Insecta. Borner considered that fossil wings did not have much value in insect systematics, and, in any case, there were far too few fossils for paleontology to have much bearing on classification. Comparative anatomical studies of recent forms, Borner argued, would give a more accurate picture. Borner, whose system was widely accepted, arranged the 19 orders of winged insects that he recognized in five sections. Three of these correspond with the "paleopteran orders," "orthopteroid orders," and "hemipteroid orders" recognized today. In other words, Borner correctly assigned the Corrodentia, Mallophaga, and Siphunculata with the Hemiptera. The two remaining sections contained the endopterygote orders, though Borner's ideas on their affinities were to be shown by Tillyard (see below) to be incorrect.

Comstock (1918, and earlier), an American entomologist, supported Brauer's arrangement as a result of his comparative studies of the wing venation of living insects. Comstock was the first person to make extensive use of wing venation in determining affinities. He emphasized, however, that classifications should be based on many characters and not wings alone.

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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