The Wax Moth: A Problem or a Solution?

Galleria mellonella L. (Greater Wax Moth) and Achroia grisella E (Lesser Wax Moth) are honey bees' most disastrous and economically important pests. Furthermore, in comparison to adults, larvae are a primary destructive stage for honey bee colonies. Voraciously feeding larvae prefer to take bee combs, stored pollen reserves, honey, larval and pupal exuviate, slum gum of the hive, wax capping, natural bee wax, and queen-rearing material containing wax in the storage. Larvae bore the hive, constructing silken tunnels in the colony combs to feed on stored products in the hive. The infested combs become covered with a mass of webbing and faecal matter that results in the condition of gallariasis. Weaker, queen-less, poorly managed, less ventilated colonies and abandoned bee hives become easy targets of wax moth infestation. Further, the strong colonies are also prone to infestation, being a potential host for the heavy growth of this destructive breeder pest. However, after infestation, the bee population of strong colonies declines quickly, and eventually, the hive is destroyed. The present chapter highlights the introduction of the concerned disastrous pest, morphology, development, mating, reproduction, and control. The wax moth is considered a problem by apiarists. In contrast, while considering other characteristic features of this insect, the potential ability to degrade plastic of variant types, it provides an excellent solution to increasing plastic pollution. Considering both characteristics of this insect, the present book is titled 'Wax Moth a Problem or Solution?

The two predominant wax moth species, the greater and the lesser wax moths, exhibit remarkably different morphometric characteristics in the egg, larva, pupa, and adult stages. The eggs of the greater wax moth (GWM) are pink, cream or white, with an ellipsoid, ovoid or obovoid shape, whereas the eggs of the lesser wax moth (LWM) are creamy-white with a spherical shape. Furthermore, in the GWM, the egg size range is 0.44 ± 0.04 × 0.36 ± 0.02 mm, while in the LWM, the egg size corresponds to 0.41 ± 0.02 × 0.31 ± 0.01 mm. The first instar larval length in the GWM is 1-3 mm, whereas the last instar body length corresponds to 12-20 mm. In the case of LWM, the first instar of body measurement is 1-20 mm, while in the last instar, it grows upto18.8 ± 0.4 mm. The pupal size in the GWM; is 12-20 mm in length and 5-7 mm in width, while the pupa in the LWM is 11.3 ± 0.4 mm in length and 2.80 ± 1.89 mm in width. Similarly, in the LWM, the adult body is 10 mm long in the male and 13 mm long in the female moths. The GWM adults possess a 15 mm body length. The dimensions mentioned above for the GWM and the LWM elucidate that the various developmental stages are distinguishable. The present chapter is attributed to the external body dimension and characteristic features of two predominant types of wax moths, which impose significant challenges to apiculture. 

The wax moth (WM) is a holometabolous insect with developmental stages of egg, larva, pupa, and adult in its life cycle. The development coherence of the wax moth is influenced by different abiotic and biotic environmental cues, including the larval diet, temperature, cannibalism, genomic content, insect hormones, and pheromones. The fecundity and fertility are comparatively high in WM to ensure species' survival within the honey bee hive. The wax moth adults preferentially infest the weaker colonies at night, where they live in the concealed space, usually on the top bar of the wooden chamber. Mating usually takes place on nearby trees; after that, the gravid female enters the hive to oviposit in the crevices and cracks to hide from the host honey bees. Afterward, the eggs hatch into the larva that feeds on the bee wax, honey, pollen, and exuviate of the honey bees. Severe localised concealing sites of WM in the hive facilitate specific pest protection in the host honey bee colony, eventually destroying the entire hive and forcing the honey bees to abscond the hive. The present chapter elucidates the development of a specific devastating pest of honey bee colonies, including influential abiotic and biotic factors. Furthermore, the differentiation of the life cycles of the greater wax moth (GWM) and the lesser wax moth (LWM) is also speculated in detail as per available literature.

The wax moth male secretes various pheromones to attract the female for mating. The volatiles induce species-specific influence, which modulates the behaviour of other members of the same species. The primary pheromones include nonanal and undecanal, hexanal, heptanal, octanal, decanal, undecanol, and 6, 10, 14 - trimethylpentadecanon-2. The specific chemicals are secreted by a pair of glands on the forewings of the male moth in the greater and lesser wax moth. These volatiles are essential for the adult stage and plays a critical role in larval and pupal aggregation. The specific chapter elaborates on the chemical composition of the pheromones, their influence on the conspecific individuals, and their role in modulating the mating behaviour, in the case of the greater wax moth (GWM) and the lesser wax moth (LWM).

The wax moth adults prefer to mate on trees near the bee farm. For mating, they exhibit a specific behavioural pattern that includes the male's production of ultrasonic sound waves, wing vibration by the female moth, and pheromonal release by the male moth. After mating, the gravid female returns to the hive and oviposits there. The pairing in this moth occurs in a sex–role reversal manner rather than the typical moth signalling system. The male moth produces ultrasonic sound and pheromonal signals in this insect, whereas females have chemical signals in other moths. In other words, pairing in the wax moth occurs by releasing pheromones and wing fanning, attracting female moths with a response to wing fanning. Furthermore, the presence of the female moth induces the male to produce ultrasonic sounds that attract the female and make her receptive to courtship. The current chapter elucidates signalling in the male wax moth, the response of the female exclusively to the male's mating calls and volatiles released by the male to guide her for the mating. Comparatively, more detailed information is available on the greater wax moth (GWM) than, the lesser wax moth (LWM) concerning insect biology, laboratory rearing, morphology, anatomy, physiology, genomics, proteomics, mating, reproduction, immunity, and plastic degradation capacity.

The wax moth infestation can be controlled with various physical, chemical, and biological methods. As the wax moth is a typical lepidopteran insect that is poikilothermic, exposing multiple developmental stages and imagoes to extremely low and higher temperatures can provide a solution for the specific pest infestation. Additionally, divergent pesticides targeting the nervous system, respiratory system, developmental regulation, and general insect physiology further solve the problem. The biological control measures include the application of various micro-organisms or their secreted products that can help regulate the insect population. The present chapter highlights primary methods for regulating the wax moth infestation with divergent strategies to reduce economic loss to apiculture.

Environmental pollution due to plastic is becoming a concentration, drawing concern throughout the world. The wax moth larvae possess the potential for biodegradation of different types of plastic with or without the involvement of the intestinal microbiome in the larval gut. Similarly, mealworms and Tenebrio molitor have been reported to cause the degradation of polyethene and polystyrene mixtures. According to scientific literature, superworms such as Zophobas atratus can cause polystyrene degradation. The plastic is biodegradable with many bacterial genera, including Pseudomonas, Ralstonia, Stenotrophomonas, Rhodococcus, Staphylococcus, Streptomyces, Bacillus, Aspergillus, Cladosporium, Penicillium, and others. A few other invertebrates with complex gut microbiomes also possess this property of plastic biodegradation.