The Australian insect fauna is highly endemic and characterised by numerous unique higher‐level taxa. In addition, a number of groups are noticeably absent or depauperate on the continent. Many groups found in Australia show characteristic Gondwanan distribution patterns on the southern continents. There are extensive radiations on the plant families Myrtaceae and Mimosaceae, a specialised arid/semiarid fauna, and diverse taxa associated with rainforests and seasonally wet tropical regions. The fauna is also poorly studied, particularly when compared with the flora and vertebrate groups. However, studies in the last two decades have provided a more comprehensive picture of the size of the fauna, relationships, levels of endemism, origins and its evolution. Here we provide an overview of these and other aspects of Australian insect diversity, focusing on six groups, the Thysanoptera and the five megadiverse orders Hemiptera, Coleoptera, Diptera, Lepidoptera and Hymenoptera.

Many hemipteroids are major pests and vectors of microbial pathogens, infecting crops. Saliva of the hemipteroids is critical in enabling them to be voracious feeders on plants, including the economically important ones. A plethora of hemipteroid salivary enzymes is known to inflict stress in plants, either by degrading the plant tissue or by affecting their normal metabolism. Hemipteroids utilize one of the following three strategies of feeding behaviour: salivary sheath feeding, osmotic-pump feeding and cell-rupture feeding. The last strategy also includes several different tactics such as lacerate-and-flush, lacerate-and-sip and macerate-and-flush. Understanding hemipteroid feeding mechanisms is critical, since feeding behaviour directs salivary composition. Saliva of the Heteroptera that are specialized as fruit and seed feeders, includes cell-degrading enzymes, auchenorrhynchan salivary composition also predominantly consists of cell-degrading enzymes such as amylase and protease, whereas that of the Sternorhyncha includes a variety of allelochemical-detoxifying enzymes. Little is known about the salivary composition of the Thysanoptera. Cell-degrading proteins such as amylase, pectinase, cellulase and pectinesterase enable stylet entry into the plant tissue. In contrast, enzymes such as glutathione peroxidase, laccase and trehalase detoxify plant chemicals, enabling the circumvention of plant-defence mechanisms. Salivary enzymes such as M1-zinc metalloprotease and CLIP-domain serine protease as in Acyrthosiphon pisum (Aphididae), and non-enzymatic proteins such as apolipophorin, ficolin-3-like protein and 'lava-lamp' protein as in Diuraphis noxia (Aphididae) have the capacity to alter host-plant-defence mechanisms. A majority of the hemipteroids feed on phloem, hence Ca++-binding proteins such as C002 protein, calreticulin-like isoform 1 and calmodulin (critical for preventing sieve-plate occlusion) are increasingly being recognized in hemipteroid-plant interactions. Determination of a staggering variety of proteins shows the complexity of hemipteroid saliva: effector proteins localized in hemipteran saliva suggest a similarity to the physiology of pathogen-plant interactions.

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The antennal sense organs of four Australian spittlebugs, Aufidus trifasciatus Stål, Euryaulax carnifex (Fabricius), Petyllis deprivata (Walker) and Tonnoiria tasmaniae Lallemand (Hemiptera: Cercopidae) are described for the first time, based on scanning electron microscope observations. Four major types of sense organs were found: one basiconic sensillum and 8-9 coeloconic sensilla on the expanded flagellar base, and several trichoid sensilla and one campaniform sensillum on the pedicel. The antennal sensilla found in the four species show very similar patterns in their shape, distribution and arrangement and this suggests that the genera Aufidus Stål, Petyllis Kirkaldy and Tonnoiria Lallemand, all currently placed in the Afrotropical and Oriental tribe Rhinaulacini, may belong to the Australian tribe Euryaulacini. In addition, the history of the nomenclature of two Australian species previously assigned to the genus Eoscarta is reviewed, and the following two resurrected combinations established: Euryaulax carnifex (Fabricius) comb. rev. and Euryaulax vacuola (Jacobi) comb. rev.

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