Insect protective waxes

Sesterterpenes, C25 terpenoids, are relatively uncommon, primarily fungal metabolites, although some compounds of this series are known from higher plants and others from insect protective waxes (Cordell, 1974 Crews and Naylor, 1985 Hanson, 1972). The principal type of sesterterpenes includes the fungal metabolites known as ophiobolanes. Two... 

Furthermore, sesterterpenes are relatively abundant in sponges in contrast with their very limited distribution elsewhere in insect protective waxes and fungi [the reviews of McCrindle and Overton 135) and Hanson (772) may be consulted]. 

A few insecticides interfere mechanically with the insect s functions. For example, mineral oils suffocate insects silica dusts destroy their body water balance by damaging their protective wax covering. 

Other evidence suggests that superficial waxes may play a part in the repellency of some plants to insects.These waxes also may be involved in the control of leaf temperature and the protection of leaf tissues from ultra-violet radiation. 

Waxes are more brittle, harder, and less greasy than fats. They are used to make polishes, cosmetics, ointments, and other pharmaceutical preparations, as well as candles and phonograph records. In nature, waxes coat the leaves and stems of plants that grow in arid regions, thus reducing evaporation. Similarly, insects with a high surface-area-to-volume ratio often have a coating of a natural protective wax. 

Waxes are found in animal and insect secretions and the cell walls of some bacteria. The stored fat of marine animals has a high wax component which forms an energy reserve. Waxes are extracted and used commercially in the preparation of creams, cosmetics, polishes, lubricants and protective coatings for surfaces. 

The composition of beeswax varies by insect species and by what the bees have been eating. Beeswax has a low melting point, and is often cast into useful or decorative shapes. Combined with resins, it was used as a water-proofing and adhesive. It has been used as a coating on paintings and furniture, to enhance the appearance of and to protect the surfaces from moisture. It was used as a water-repellent and adhesive in ships and boats. Beeswax has been applied to fabric, cordage, and hair to add luster and increase water-resistance, and as a base for cosmetic and medicinal creams and lotions. Beeswax was the primary and best available material for making candles until the invention of paraffin wax, which is a by-product of the distillation of petroleum. 

I. Epidermis, of a single layer of epidermal cells whose outer walls are strongly cutinized. Cutin is a wax-like substance which forms a protective coat to the epidermis, preventing the evaporation of water, the ingress of destructive parasites, and injury from insects. 

Waxes are esters between fatty acids and high molecular alcohols such as cetyl- or myricyl alcohol. Waxes occur in plants as a coating on the epidermis on leaves and fruits with the function to protect against loss of water. Also, insects such as bees produce waxes. 

Waxes are common in living organisms. The feathers of birds are coated with wax to make them water repellent. Some vertebrates secrete wax in order to keep their fur lubricated and water repellent. Insects secrete a waterproof, waxy layer on the outside of their exoskeletons. Wax is also found on the surfaces of certain leaves and fruits, where it serves as a protectant against parasites and minimizes the evaporation of water. 

Propolis (registration number chemical abstracts service - CAS 9009-62-5) is a sticky colored material, which honeybees collect from different plants exudates and modify in its hypopharyngeal glands, being used in the hive to fill gaps and to protect against invaders as insects and microorganisms. Raw propolis usually contains 50% resin and balsam, 30% wax. 

The arthropods, especially the insects, exhibit probably the greatest ability to synthesize and utilize alkanes of any class of the Animal Kingdom. Their external surfaces are covered with cuticular waxes that provide a barrier which is impervious to water and prevents invasion by micro-organisms as well as providing general protection. This barrier may also effect (both positively and negatively) the penetration of insecticides. The waxes contain a wealth of hydrocarbons with n-alkanes sometimes predominating. Over one-hundred hydrocarbons have also been isolated and characterized from internal... 

The cuticular waxes of insect species may contain the following chemical classes hydrocarbons, fatty acids, alcohols, triacylglycerols and wax esters (Golgbiowski et al., 2011 Nelson Blomquist, 1995). The waxes of some species also contain aldehydes, ketones, esters and sterols. The wax compositions of insects can vary depending on stage, sex, age, and their position in the colony hierarchy. Cuticular waxes can also vary within species as a response to living conditions such as temperature, dryness and available food. The major function of insect waxes is protection against desiccation, but they also prevent microbial infections, affect the adsorption of chemicals and play a role in chemical communication... 

Surface waxes serve a number of functions usually associated with protection. In plants and insects they prevent desiccation and in birds they serve to waterproof feathers. While a few components present in surface lipids can prevent growth of pathogens, the total surface wax layer certainly functions to prevent microbial entry into the organism. Some surface lipids serve as chemical communicants such as the hydrocarbon sex attractants and kairomone of insects. Although internal waxes are infrequently found in Nature, where they do occur they act as energy storage (e.g. in jojoba seeds or marine organisms). For a fuller review of all aspects of natural waxes refer to Kolattukudy (1976). 

Some nest parasites in social insects are protected because their cuticular chemistry is very similar to that of the hosts. The complex cuticle hydrocarbon blends of parasite and host are virtually identical and the hosts cannot distinguish the parasites from conspecifics (Stowe, 1988). Nest parasites of the genus Trichopsenius biosynthesize their hydrocarbon mixture the pattern matches the species-specific mixture of their termite hosts. In contrast, the scarabaeid beetle, Myr-mecaphodius excavatacollis, which associates with ants, acquires its hydrocarbons by association with the host and can invade the nests of several different species of ants with different hydrocarbon blends (Stowe, 1988). In another bizarre example, larvae of the neuropteran, Chrysopa slosso-nae, cover themselves with wax plucked from their wax-coated aphid prey. The ants that tend these aphids fail to recognize the neuropterans and do not attack them (Stowe, 1988). 

Fine alumina dust is also insecticidal. When larvae crawl over wet dust there is no effect because moisture is present. However, the skin has lost its oily protection by adsorption on the alumina and the insect dries out and dies quickly when placed in dry air (165). A combination of aerogel and ammonium fluorosilicate was especially effective for controlling mites on caged reptiles (166). Silica gel insecticides killed DDT-resistant mosquitoes (167) boric acid-modified silica aerogel was effective against cockroaches, and it was lethal even when their mouths were waxed shut so they could not eat it (168, 169). 

The main significance of waxes is that they form a hydrophobic layer on the surface of organisms. In animals these occur in the skin, hair, fur or feathers, while in plants they are found in the surface layers of leaves, fruits and other aerial (above ground) parts. They act mainly to control transpiration, preventing water loss by evaporation, and protecting the organisms against environmental influences, insects and parasites. 

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