This review summarizes which body parts have taste function in which insect taxa. Evidence of taste by mouthparts, antennae, and tarsi is widespread. Mouthparts that commonly have taste function are the labium, including the labella and labial palps, the maxillae, including the galeae and maxillary palps, the inner surface of the labrum or clypeolabrum of chewers, and inside the precibarium/cibarium of hemipterans, which have piercing-sucking mouthparts. Tasting with mandibles has not been found, and tasting with the hypopharynx is seldom reported. Use of the antennae appears uncommon among fly species, but common among species of lepidopterans, hymenopterans, beetles, and bugs. Although tasting with legs, especially tarsi, is reported mostly for fly and lepidopteran species, there is also evidence of it for multiple species of beetles, grasshoppers, and hemipterans, and one species of a roach, an ant, and a bee. Ovipositor taste function has been supported for some species of flies, lepidopterans, hymenopterans, orthopterans, and odonates. Taste by wings has been much less studied, but has been documented in a few fly species. Taste remains unstudied for any species or any body parts of Archaeognatha, Dermaptera, Mantodea, Mecoptera, Phasmatodea, Megaloptera, Neuroptera, Phthiraptera, Psocoptera, Siphonaptera, as well as Raphidioptera, Strepsiptera, Embioptera, Notoptera, and Zoraptera. Across holometabolous insects, larvae have not often been examined, the exception being some species of lepidopterans, flies, and beetles. Taste studies of antenna and legs are uncommon for even lepidopteran and beetle larvae.

Insect antennae are crucial sensory organs that house numerous sensilla with receptors for perceiving a wide variety of cues dominating their world. Historically, inconsistent terminology and criteria have been used to classify antennal sensilla, which has greatly impeded the comparison of data even across closely related species. Longhorn beetles (Coleoptera: Cerambycidae) are no exception to this quandary, and despite their prominent antennae, few studies have investigated their antennal morphology and ultrastructure, and none have compared sensillar diversity and variation among cerambycids. Existing studies of longhorn beetle antennal sensilla include only 29 species in five of the eight cerambycid subfamilies and include misidentified sensilla types and conflicting terminology. As such, it is very difficult to conduct comparative morphological studies of antennal sensilla in longhorn beetles and challenging to understand inter- and intra-specific variation in the sensory systems of these beetles.To facilitate future comparative studies, we reviewed all accessible published papers that have used scanning and transmission electron microscopy (SEM and TEM) to investigate antennal sensilla in cerambycids, and present a first attempt at standardizing the classification of their documented sensilla types and subtypes. Specifically, we discuss seven major types of antennal sensilla (Boöhm bristles, sensilla chaetica, chemosensory hairs, sensilla basiconica, dome shaped organs, sensilla coeloconica, and sensilla auricillica). We also imaged the antennae of relevant species of longhorn beetles using SEM and included images exemplifying as many of the sensilla types and subtypes as possible.

On the basis of biological activities of the ethyl acetate extracts of four Xenorhabdus sp., including Xenorhabdus nematophila FUM 220, Xenorhabdus nematophila FUM 221, Xenorhabdus bovienii FUM 222, and Xenorhabdus bovienii FUM 223, X. nematophila FUM 220 was preferentially selected to track the isolation of responsible compounds. Chemical study on the ethyl acetate extract of X. nematophila isolate FUM220 which is derived from the native nematode Steinernema carpocapsae (Rhabditida: Steinernematidae), was evaluated, and eleven compounds, including xenocoumacin II (1), xenortide-396 (2), xenortide A (3), xenortide-410 (4), xenortide-449 (5), xenematide A 663 (6), rhabdopeptide-574 (7), rhabdopeptide-588 (8), rhabdopeptide-687 (9), rhabdopeptide-701 (10), and nematophin-273 (11) were characterized. In this experimental study, we surveyed the antitumoral potential of bacterial extract and bacterial metabolites to treat human breast cancer (MCF-7), human lung cancer (A549), and murineTumor (B16) cell lines. We observed that all samples were cytotoxic, but bacterial extracts of X. nematophila FUM 220 and X. bovienii FUM 223 showed higher toxicity on mentioned cell lines. Potent cytotoxic activity was found for compounds 6 and 11 with IC₅₀ of 6.2 µg/ml against human lung cancer A549 cell lines, too.These compounds showed moderated antibacterial activity against Xanthomonas oryzae pv. oryzae strain Xoo-IR42 (Xanthomonadales: Xanthomonadaceae) (MIC of 62.5 µg/ml) and Staphylococcus aureus strain 1112 (Bacillales: Staphylococcaceae) (MIC of 100 µg/ ml). The bacterial extracts from X. bovienii FUM 222 showed strong inhibition of the growth of S. aureus strain 1112, by a minimal inhibitory concentration assay (MIC of 53.5 µg/ml). Xenorhabdus genera produce metabolites with potent cytotoxic and antibacterial activity. Single compounds can be isolated, identified, and commercialized, but various species or strains may change their anticancer or antimicrobial potential. The present study brings new clues regarding the qualified of Xenorhabdus as future peptide sources for supplying natural bioactive compounds and challenge multidrug-resistant bacteria, treat cancer, and plant diseases.

Graphical Abstract

Using seventeen-year records of daily light trap catches of predatory Neuroptera (Chrysopidae, 13 species) and Coleoptera (Coccinellidae, 10 species), and of phytophagous Lepidoptera (Noctuidae, 79 species) we tested a hypothesis predicting that the range of annual fluctuations of catch size is greater in aphidophages, whose diet occurs irregularly and locally, than in phytophages, whose diet is available regularly and abundantly.The ranges of fluctuations of annual catches measured as the coefficient of variance (standard deviation expressed as a percentage of the average) of detrended annual catches were significantly greater in Chrysopidae (84 ± 7.1%) and Coccinellidae (121 ± 14.0%) than in Noctuidae (66 ± 2.6%). The difference between aphidophages and phytophages remained when we tested differences between the former and the samples of Noctuidae consisting only of those species whose characteristics (abundance, length and timing of flight period, number of generations per season, overwintering stage) were the same as in aphidophages. Similarly, no differences were found between sets of Noctuidae species that have characteristics (abundance, voltinism, period of flight activity) similar to aphidophages and sets of Noctuidae species that have contrary characteristics. Flight abilities of aphidophages are smaller than those of Noctuidae. As a result of this difference a light trap collects populations of aphidophages from a smaller area than populations of Noctuidae.Thus the extent of fluctuations of catch size of aphidophagous and phytophagous species is influenced both by annual differences in food availability and by differences in size of the area from which the individuals assembling to the light source are recruited.