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Fig. 2.18 The mouthparts and feeding currents of a mosquito larva of Anophelesquadrimaculatus (Diptera: Culicidae). (a) The larva floating just below the water surface, with head rotated through 180° relative to its body (which is dorsum-up so that the spiracular plate near the abdominal apex is in direct contact with the air). (b) Viewed from above showing the venter of the head and the feeding current generated by setal brushes on the labrum (direction of water movement and paths taken by surface particles are indicated by arrows and dotted lines, respectively). (c) Lateral view showing the particle-rich water being drawn into the preoral cavity between the mandibles and maxillae and its downward expulsion as the outward current. ((b,c) After Merritt et al. 1992.)

A unique modification of the labium for prey capture occurs in nymphal damselflies and dragonflies (Odonata). These predators catch other aquatic organisms by extending their folded labium (or "mask") rapidly and seizing mobile prey using prehensile apical hooks on modified labial palps (Fig. 13.4). The labium is hinged between the prementum and postmentum and, when folded, covers most of the underside of the head. Labial extension involves the sudden release of energy, produced by increases in blood pressure brought about by the contraction of thoracic and abdominal muscles, and stored elastically in a cuticular click mechanism at the prementum-postmentum joint. As the click mechanism is disengaged, the elevated hydraulic pressure shoots the labium rapidly forwards. Labial retraction then brings the captured prey to the other mouthparts for maceration.

Filter feeding in aquatic insects has been studied best in larval mosquitoes (Diptera: Culicidae), black flies (Diptera: Simuliidae), and net-spinning caddisflies (Trichoptera: many Hydropsychoidea and Philopota-moidea), which obtain their food by filtering particles (including bacteria, microscopic algae, and detritus) from the water in which they live. The mouthparts of the dipteran larvae have an array of setal "brushes" and/or "fans", which generate feeding currents or trap particulate matter and then move it to the mouth. In contrast, the caddisflies spin silk nets that filter par-ticulate matter from flowing water and then use their mouthpart brushes to remove particles from the nets. Thus insect mouthparts are modified for filter feeding chiefly by the elaboration of setae. In mosquito larvae the lateral palatal brushes on the labrum generate the feeding currents (Fig. 2.18); they beat actively, causing particle-rich surface water to flow towards the mouth-parts, where setae on the mandibles and maxillae help to move particles into the pharynx, where food boluses form at intervals.

In some adult insects, such as mayflies (Ephemer-optera), some Diptera (warble flies), a few moths (Lepidoptera), and male scale insects (Hemiptera: Coccoidea), mouthparts are greatly reduced and nonfunctional. Atrophied mouthparts correlate with short adult lifespan.

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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