Paleoptera

are visible with segments 1-8 bearing spiracles. In male Odonatathe sternum of segment 2 is grooved and that of segment 3 bears copulatory structures used in the transfer of sperm to (sometimes also from) the female genital tract. The true genital opening is located behind the ninth sternum. In female Zygoptera and many Anisoptera that are endophytic (lay their eggs into plant tissues) a well-developed ovipositor is present. In exophytic Anisoptera it is reduced or absent.

Most internal organs are greatly elongated because of the narrow body. The testes extend from abdominal segments 4-8 and the ovaries occupy the whole length of the abdomen. Between 50 and 70 Malpighian tubules, united in groups of 5 or 6, enter the alimentary canal at the junction of the midgut and hindgut. The respiratory system is well developed and in many species includes a large number of air sacs in the thoracic region. The nervous system is generally primitive, although the brain is enlarged transversely due to the presence of large optic lobes.

Larva. Odonate larvae are usually shorter and stockier than adults. In general the larval head resembles that of the adult, though it differs in possession of the "mask," the elongated labium (Figure 6.8), used to capture prey. At rest the mask (so-called because it often covers the other mouthparts) is folded at the junction of the postmentum and prementum and held between the bases of the legs. It is extended extremely rapidly (in about 16-25 msec) by means of localized blood pressure changes, assisted by the release of tension in the labial locking muscles, and the prey is grasped by the labial palps. In contrast to those of adults, the legs are normally positioned on the thorax, well developed and quite long. At the tip of the abdomen there are three appendages, one mediodorsal and two lateral (the cerci). These are small in Anisoptera but enlarged to form caudal lamellae in Zygoptera.

Internally larvae differ from adults in several features. In the foregut there is a well-developed gizzard for breaking up food. There are initially only a few Malpighian tubules, though the number increases in each instar. In all odonate larvae, some gaseous exchange takes place directly across the body wall, including the wing pads, and via the wall of the rectum. In addition, larvae have special respiratory structures. In Anisoptera the wall of the rectum is greatly folded and well supplied with tracheae, forming "rectal gills." Water

FIGURE 6.8. Lateroventral view of head of dragonfly larva showing mask. [After A. D. Imms, 1957, A General Textbook of Entomology, 9th ed. (revised by O. W. Richards and R. G. Davies), Methuen and Co.]

FIGURE 6.8. Lateroventral view of head of dragonfly larva showing mask. [After A. D. Imms, 1957, A General Textbook of Entomology, 9th ed. (revised by O. W. Richards and R. G. Davies), Methuen and Co.]

138 is continually pumped in and out of the rectum. Interestingly, the musculature used to ventilate the rectal gills serves also to jet propel the larva in swimming and to extend the labium for prey capture! In Zygoptera the caudal lamellae appear to supplement the surface area available for gaseous exchange (although in highly oxygenated water larvae appear to survive perfectly well when the lamellae are removed). In a few Zygoptera paired gills occur on most abdominal segments, while in Amphipterygidae filamentous perianal gills develop. (See also Chapter 15, Section 4.1.)

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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