Small hive beetle, Aethina tumida (Coleoptera: Nitidulidae): chemical profile of the cuticle and possible chemical mimicry in a honeybee (Apis mellifera) pest

The small hive beetle, Aethina tumida (Coleoptera: Nitidulidae), is an economically important pest of the Western honeybee, Apis mellifera (Hymenoptera: Apidae). We investigated the effect of rearing environment on the cuticular chemical profile of adult A. tumida, using hexane to extract the hydrocarbons and other compounds from the cuticles of beetles. Beetles were collected from A. mellifera colonies in Australia as well as reared in single sex laboratory cultures on different diets. We investigated whether rearing environment (laboratory vs. field, different apiaries, access to mating partners, diet) had any effect on cuticular hydrocarbons. Coupled gas chromatography–mass spectrometry analyses of the extracts showed that rearing environment had significant qualitative and quantitative effects on the hydrocarbons detected. The data support the hypothesis that cuticular profiles of A. tumida are contingent on environment, partitioning on the basis of rearing diet and source hives. The finding has implications for the regulation of interactions between A. tumida and honeybees and improvements in targeting of management strategies

Contrasting Micro/Nano Architecture on Termite Wings: Two Divergent Strategies for Optimising Success of Colonisation Flights

Many termite species typically fly during or shortly after rain periods. Local precipitation will ensure water will be present when establishing a new colony after the initial flight. Here we show how different species of termite utilise two distinct and contrasting strategies for optimising the success of the colonisation flight. Nasutitermes sp. and Microcerotermes sp. fly during rain periods and adopt hydrophobic structuring/‘technologies’ on their wings to contend with a moving canvas of droplets in daylight hours. Schedorhinotermes sp. fly after rain periods (typically at night) and thus do not come into contact with mobile droplets. These termites, in contrast, display hydrophilic structuring on their wings with a small scale roughness which is not dimensionally sufficient to introduce an increase in hydrophobicity. The lack of hydrophobicity allows the termite to be hydrophilicly captured at locations where water may be present in large quantities; sufficient for the initial colonization period. The high wettability of the termite cuticle (Schedorhinotermes sp.) indicates that the membrane has a high surface energy and thus will also have strong attractions with solid particles. To investigate this the termite wings were also interacted with both artificial and natural contaminants in the form of hydrophilic silicon beads of various sizes, 4 µm C18 beads and three differently structured pollens. These were compared to the superhydrophobic surface of the planthopper (Desudaba psittacus) and a native Si wafer surface. The termite cuticle demonstrated higher adhesive interactions with all particles in comparison to those measured on the plant hopper

Ultrastructure of the eggs of Culicoides molestus (Diptera: Ceratopogonidae)

The eggs of Culicoides molestus (Skuse) are described and illustrated by scanning and transmission electron microscopy. Eggs are elongate with a slight dorsoventral curvature. No outer chorionic tubercles are present. Aeropyles are present in large numbers at the anterior end and in lower numbers at the posterior end and lateral regions. The chorion has 5 layers. An outer, rough, proteinaceous layer covers a smoother inner surface, which in turn encloses a layer of columns and meshwork that appears capable of containing air. These columns are underlain by an additional 2 layers. The aeropylar region, in combination with the chorionic meshwork, appears to provide a plastron that may aid in the survival and development of inundated eggs

Morphology and ultrastructure of the anterior adhesive areas of the capsalid monogenean parasites Benedenia rohdei from the gills and B. lutjani from the pelvic fins of Lutjanus carponotatus (Pisces: Lutjanidae)

The anterior adhesive areas of Benedenia rohdei from the gills and B. lutjani from the pelvic fins of Lutjanuscarponotatus at Heron Island, Australia, were studied using scanning and transmission electron microscopy. All specimens were fixed when detached from host tissue. Both monogenean species have two disc-like anteroventral attachment organs, each of which has an anterolateral adhesive area divided into three adjacent zones by tegument from the ventral surface of the attachment organ. A rod-shaped secretion and a smaller, roughly spherical secretion are associated with the anterior adhesive areas in both species; a third type of secretion occurs anteriorly but outside these adhesive areas. The electron-dense spherical secretory bodies released onto the anterior adhesive zones in these Benedenia spp. are of a single type and differ ultrastructurally from those previously reported in monogeneans living on teleost hosts. A correlation, therefore, between secretion morphology and host type is not supported. No relationship was found between parasite microhabitat and secretion morphology

Influence of rearing hosts on host size acceptance by Trichogramma australicum

We investigated the acceptance of different sized host models by Trichogramma australicum in the laboratory. We used isoline cultures of T. australicum reared in hosts of different sizes. Helicoverpa armigera represent relatively large hosts, and those of Sitotroga cerealella are small, termed the Ha and Sc biotypes, respectively. Five sizes of glass beads were tested for acceptance: diameter 0.5, 0.75, 1.0, 1.5 and 2.0 mm. The acceptance of a host model was determined by persistent attempted drilling of a glass bead by a female. The relationship between host egg size and number of eggs laid by a female was also investigated. We used three sizes of artificial egg (diameter 0.75, 1.00, and 1.50 mm of hemispherical cupules) each containing artificial diet. Ha biotype wasps accepted host models in the range 0.75-1.50 mm dia. (vol. 0.166-1.325 mu l), whereas those of the Sc biotype accepted host models in the range 0.50-1.00 mm dia. (vol. 0.05-0.393 mu l). This evidence suggests a lineal (possibly genetic) influence to host size acceptance for T. australicum, dependent on the size of the host in which the wasp has been reared. Also T. australicum lay fewer eggs in smaller artificial eggs than in larger ones. The role of host size in host acceptance and number of eggs delivered, and its implications, is discussed

Glands associated with the anterior adhesive areas of the monogeneans, Entobdella sp. and Entobdella australis (Capsalidae) from the skin of Himantura fai and Taeniura lymma (Dasyatididae)

Using scanning and transmission electron microscopy, investigations were carried out on the anterior adhesive areas of Entobdella sp. from the skin of Himantura fai and Entobdella australis from the skin of Taeniura lymma at Heron Island, Australia. All studies were of parasites detached from either host tissue or a substrate. Both species of monogeneans have two characteristic anteroventral adhesive pads, one on either side of the head, subdivided to form a 'diadem'. Two types of gland cells are associated with the anterior adhesive areas in both species and each cell type produces a different secretion: a rod-shaped secretion and a smaller, roughly spherical secretion. Each secretion type differs in electron-density, with those putatively in the process of formation being less electron-dense. Both types of secretory bodies are membrane-bound. Microtubules are evident around forming rod-shaped bodies. The bounding membranes of the rods of both species show a periodic banding of approximately 12 nm. Both types of secretion are present at the surface of the adhesive pads in specimens of Entobdella sp. fixed when detached from the host. The secretory bodies observed in Entobdella sp. and E. australis from rays show some differences to those reported from Entobdella soleae, a parasite of a flatfish teleost. Other ultrastructural differences also exist. We conclude that the types of adhesive secretory bodies may remain constant within genera providing the hosts are similar

Aedes aegypti: Sensilla trichodea and stimulus-conducting structures

Much of the morphology of the olfactory sensilla on the antennae of the mosquito Aedesaegypti (L.) has been described, however little is known about the fate of odour molecules once they have been adsorbed onto the surfaces of sensilla. A stimulus-conducting system of pores, pore kettles, and pore tubules has been described for the sensillatrichodea (olfactory hairs) of several insects but not mosquitoes. Scanning electron microscopy was used to identify the s. trichodea of Ae. aegypti and to attempt visualization of their pore openings. Chemical fixation, cryopreparation, freeze drying, and negative staining, with high resolution transmission electron microscopy (TEM), were used to locate putative stimulus-conductingstructures associated with the pores. TEM sections using Dalton's fixative or freeze drying showed pores and pore tubules, whereas pore tubules were poorly preserved in cryoprepared sections. The putative stimulus-conductingstructures were clearly demonstrated by negative staining of whole sensilla which was quick and easy. The current hypothesis of olfactory stimulus conduction is extended to include Ae. aegypti

The comparative morphology of epidermal glands in Pentatomoidea (Heteroptera)

The Heteroptera show a diversity of glands associated with the epidermis. They have multiple roles including the production of noxious scents. Here, we examine the cellular arrangement and cytoskeletal components of the scent glands of pentatomoid Heteroptera in three families, Pentatomidae (stink bugs), Tessaratomidae, and Scutelleridae (shield-backed bugs or jewel bugs). The glands are; (1) the dorsal abdominal glands, (2) the tubular glands of the composite metathoracic gland, and (3) the accessory gland component of the composite metathoracic gland. The dorsal abdominal glands are at their largest in nymphs and decrease in size in adults. The metathoracic gland is an adult-specific gland unit with a reservoir and multiple types of gland cells. The accessory gland is composed of many unicellular glands concentrated in a sinuous line across the reservoir wall. The lateral tubular gland is composed of two-cell units. The dorsal abdominal glands of nymphs are composed of three-cell units with a prominent cuticular component derived from the saccule cell sitting between the duct and receiving canal. The cuticular components that channel secretion from the microvilli of the secretory cell to the exterior differ in the three gland types. The significance of the numbers of cells comprising gland units is related to the role of cells in regenerating the cuticular components of the glands at moulting in nymphs

The role of micro/nano channel structuring in repelling water on cuticle arrays of the lacewing

Non-wetting surfaces help in the survival of terrestrial and semi-aquatic insects. Some insects encounter wetting by rain, through contact with water collected on foliage, or in ponds, rivers or streams. There is an evolutionary pay-off for such insects to adopt hydrophobic structuring especially on regions that contact water, such as legs or large surface areas such as wings. Here we investigate lacewings which are good candidates for getting trapped to water because of a large wing surface area-to-body mass ratio. The lacewing utilises a variety of structures/mechanisms to contend with water contact. The first level involves small hairs (macrotrichia) that project from veins on the wings and collectively hold up droplets of water above the wing surface. This defence against wetting is aided by longitudinal ridges and troughs along the hair shaft. We show, by coating single hairs with a hydrophobic polymer (similar in hydrophobicity to insect cuticle), that the channels significantly contribute to repel water droplets. Beneath the array of hairs lies a dense netting on the cuticle wing surface which reduces contact with smaller droplets. The study has implications for both insect biology and biomimetic surfaces such as light weight superhydrophobic materials

Aiming for the management of the small hive beetle, Aethina tumida, using relative humidity and diatomaceous earth

Small hive beetles (SHBs) are a global pest of European honeybee colonies. In the laboratory, the survival of adult SHBs was evaluated in relation to relative humidity (RH = 56, 64, 73, 82 and 96 %) and treatment with diatomaceous earth (DE) across 4 days. Low RH reduced survival. The application of DE reduced survival in addition to RH. Adults treated with corn flour (control) showed no difference in survival from untreated beetles. Scanning electron microscopy images showed no scarification of adult beetle cuticle after exposure to DE; therefore, water loss is likely facilitated through non-abrasive means such as the adsorption of cuticular lipids. The data agree with the hypothesis that DE causes mortality through water loss from treated insects. Egress, ingress, mortality and the egg-laying behaviours of beetles were observed in relation to a popular in-hive trench trap with and without the addition of DE. Traps filled with DE resulted in 100 % mortality of beetles compared with 8.6 % mortality when no DE was present. A simple method for visually determining beetle sex was used and documented