Terrestrial Insects

Terrestrial insects appear able to regulate their hemolymph osmotic pressure over a wide range of conditions. For example, in Tenebrio the hemolymph osmotic pressure varies only from 223 to 365 mM/l (measured as the equivalent of a sodium chloride solution) over a range of relative humidity from 0% to 100% (Marcuzzi, 1956, cited in Stobbart and Shaw, 1974). In starving Schistocerca there is only a 30% difference in hemolymph osmotic pressure between animals kept in air at 100% relative humidity and given only tap water and those kept in air at 70% relative humidity and given saline (osmotic pressure equivalent to 500 mM/l sodium chloride) to drink (Phillips, 1964a).

In terrestrial insects water is lost (1) by evaporation across the integument, although this is considerably reduced by the presence of the wax layer in the epicuticle (Chapter 11, Section 2); (2) during respiration through the spiracles [many insects possess devices both physiological and structural for reducing the loss (Chapter 15, Section 2.2)]; and (3) during excretion. Despite these adaptations, insects that inhabit extremely dry environments may become greatly dehydrated. For example, some desert beetles can survive the loss of 75% of their body water. The critical factor for these beetles is to maintain the intracellular water concentration by using the water in the hemolymph; in other words, the hemolymph form of storage excretion but an important means of conserving nitrogen in these insects whose normal diet is severely nitrogen deficient (Chapter 16, Section 5.1.1).

Temporary storage of other materials may also take place. Calcium salts (especially carbonate and oxalate) are found in the fat body of many plant-eating insect larvae. During metamorphosis they are released and dissolved, to be excreted via the Malpighian tubules in the adult. Dyes present in food are often accumulated in fat body cells where they appear to become associated with particular proteins. These proteins are then transferred to the egg during vitellogenesis and the dyes subsequently "excreted" during oviposition.

Nephrocytes (Chapter 17, Section 2) accumulate a variety of substances, especially pigments, and their name is derived from the mistaken idea that storage excretion is one of their major functions. As Locke and Russell (1998) pointed out, nephrocytes are involved in the metabolism of hemolymph macromolecules.

volume is reduced. To avoid the potential osmotic problems that this withdrawal of water creates, osmotically active particles can be excreted or rendered inactive; for example, ions are chelated and amino acids are polymerized into peptides. The strategy used appears to be correlated with the insects' diet: carnivorous species, whose food contains abundant

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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