Insect Diversity

From their beginning as primitively wingless thysanuranlike creatures, the insects have undergone a vast adaptive radiation to become the world's most successful group of living organisms. Undoubtedly, a large measure of this success can be attributed to the evolution of wings. The Paranotal Theory suggests that wings evolved from rigid outgrowths of the terga in adult insects, their initial function being the protection of the legs. Increase in the size of the paranotal lobes was associated with improvement in attitudinal control as the insects dropped from vegetation in order to escape predation. In the Paranotal Theory articulation of these winglets was a later development associated with improving attitudinal control. An idea that is becoming more popular is that wings developed from already articulated structures. These were present on all thoracic and abdominal segments in aquatic juvenile insects and from the outset were hinged in association with their function as gills, spiracular flaps, or swimming organs. Before they became large and powerful enough for true flight, the wings may have been used to propel insects over the water surface (surface skimming), as seen in some extant stoneflies and mayflies.

The Pterygota had a monophyletic origin in the Devonian and soon split into two major evolutionary lines, the Paleoptera and the Neoptera. By the late Carboniferous several distinct neopteran groups were established. These were the pliconeopterans (ple-copteroids, orthopteroids, and blattoids), which are perhaps polyphyletic, the paraneopter-ans (hemipteroids), and the oligoneopterans (endopterygotes), both of which are probably monophyletic. Of these, the endopterygotes have been by far the most successful. This is related, in large part, to the evolution of a pupal stage within the group. Various theories have been advanced for the origin of the pupal stage. The most likely theory proposes that it is equivalent to the final nymphal instar of the original exopterygote ancestor. Its initial function was to provide space for wing and wing muscle development. However, its evolution also facilitated divergence of adult and larval habits, so that the two stages no longer competed for the same resources. It also became a stage in which species could survive adverse climatic conditions, especially freezing temperatures.

Insect success (i.e., diversity) is related not only to the group's adaptability but also to the environment in which they have evolved. Being arthropods, insects possess a body plan that is superior to that of other invertebrates. They are generally small and able to fly. They usually have a high reproductive capacity, often coupled with a life history that is short and contains a pupal stage. Because of features peculiar to them, four orders (Coleoptera, Lepidoptera, Hymenoptera, and Diptera) are especially successful, comprising almost 75% of the described species. Insect evolution was coincident with the evolution of land plants. The insects were among the first invertebrates to establish themselves on land. By virtue of their adaptability they were able to colonize rapidly the new habitats formed as a result of climatic changes over the earth's surface.

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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