Like other eukaryotes, insect genomes contain a large portion of repetitive sequences, particularly transposable elements (TEs) and satellite DNAs (satDNAs). This review highlights key studies on repetitive DNAs and examines their structural, functional, and evolutionary impact in insect genomes. Repetitive sequences promote genetic diversification through mutations and large-scale rearrangements, playing a crucial role in shaping genomic architecture, aiding organismal adaptation and driving speciation. We also explore the influence of repeats in genome size variation and species incompatibilities, along with their contribution to adaptive phenotypes and gene regulation. Studying repetitive DNA in insects not only provides insights into basic genomic features but also offers valuable information for conservation strategies, pest control, and advancements in genetics, ecology, and evolutionary biology.

Bees are essential pollinators for wild, ornamental, and agricultural plants, but human activities have disrupted their habitats, threatening their persistence. Although bees face numerous challenges in habitats heavily modified by human activities, certain species persist and thrive there. This review synthesizes recent literature on two types of traits that help bees survive in human-modified environments: pre-adaptive traits, which evolved before these environments existed, and adaptive traits, which have evolved in response to new conditions. This review highlights our limited understanding of adaptive traits and examines how trait combinations, including those influenced by epigenetics, contribute to bees' success in these altered habitats. Additionally, we discuss the promising use of genomic tools to reveal signatures of adaptation in these important pollinators.

Insects exhibit remarkable adaptability to a wide range of environmental stressors, including temperature fluctuations, pathogens, and changes in diet. This adaptability is often driven by epigenetic processes, which regulate gene expression without altering the underlying DNA sequence. This review provides a comprehensive overview of these epigenetic processes in insect adaptation, highlighting their impact on development, behaviour, and stress resilience. Understanding these mechanisms is essential for pest management and conservation efforts, offering insights into the rapid adaptive capacity of insects. By examining recent studies on epigenetics in insects, we aim to elucidate the molecular underpinnings of their adaptation and suggest future research directions in this evolving field.

Female germline stem cells (fGSCs) are essential for generating mature oocytes. In general, self-renewal and differentiation of fGSCs into germ cells are regulated by niche signals from neighboring niche cells. In addition, fGSCs and their niche cells are greatly influenced by physiological and environmental factors, especially nutritional status. To clarify molecular mechanisms involved in regulating fGSC proliferation and maintenance, the fruit fly Drosophila melanogaster has served as an excellent genetic model organism. In recent years, along with sophisticated genetic tools for D. melanogaster, large-scale transcriptome, proteome, and metabolome analyses have provided new insights into D. melanogaster fGSC biology. These large-scale analyses have identified new markers and regulators for D. melanogaster fGSCs, including Netrin-A, Helical factor, eggplant, Gr43a, and genes controlling the polyol pathway, some of which are involved in nutrient-responsive control of fGSC behavior.

Currently, a wealth of genomic data is now accessible for numerous insect natural enemies, serving as valuable resources that deepen our understanding of the genetic basis of biocontrol traits in these organisms. We summarize the current state of genome sequencing and highlight candidate genes related to biocontrol traits that hold promise for genetic improvement. We also review the recent population genomic studies in biological control and the discovery of potential insecticidal genes in parasitoid wasps. Collectively, current genomic works have shown the powerful ability to identify candidate genes responsible for desirable traits or promising effectors. However, further functional study is necessary to gain a mechanistic understanding of these genes, and future efforts are also needed to develop suitable approaches to translate genomic insights into field applications.

Odors serve as important cues for many behaviors in mosquitoes, including host-seeking, foraging, and oviposition. They are detected by olfactory receptor neurons present on the sensory organs, whose axons take this signal to the antennal lobe, the first olfactory processing center in the insect brain. We review the organization and the functioning of the antennal lobe in mosquitoes, focusing on two populations of interneurons present there: the local neurons (LNs) and the projection neurons (PNs). LNs enable information processing in the antennal lobe by providing lateral inhibition and excitation. PNs carry the processed output to downstream neurons in the lateral horn and the mushroom body. We compare the ideas of labeled lines and combinatorial codes, and argue that the PN population encodes odors combinatorially. Throughout this review, we discuss the observations from Aedes, Anopheles, and Culex mosquitoes in the context of previous findings from Drosophila and other insects.

Strategies which rely on the mass-release of males to suppress mosquito populations will exert selective pressure on natural mating systems. Here we investigate how mass-releases might affect the mating behaviors of wild target populations. We highlight gaps in our understanding of both variation in these aspects of mosquito behavior and the evolutionary forces that maintain variation within and between populations. We provide a mathematical framework for integrating mosquito mating ecology into models of population suppression. Given that these strategies are being increasingly deployed, anticipating and managing evolutionary responses of target population behavior should be a priority for research.

Cuticular hydrocarbons (CHCs) play pleiotropic roles in insect survival and reproduction. They prevent desiccation and function as pheromones influencing different behaviors. While the genes in the CHC biosynthesis pathway have been extensively studied, the regulatory mechanisms that lead to different CHC compositions received far less attention. In this review, we present an overview of how different hormones and transcriptional factors regulate CHC synthesis genes, leading to different CHC compositions. Future research focusing on the regulatory mechanisms underlying CHC biosynthesis can lead to a better understanding of how insects could produce dynamic chemical profiles in response to different stimuli.

The circadian rhythm of adult emergence (aka eclosion) of the fruit fly Drosophila is a classic behavioural read-out that served in the first characterisation of the key features of circadian clocks and was also used for the identification of the first clock genes. Rhythmic eclosion requires the central clock in the brain, as well as a peripheral clock in the steroidogenic prothoracic gland. Here, we review recent findings on the timing and neuroendocrine coupling mechanisms of the two clocks. These findings identify rhythmic prothoracicotropic hormone and downstream ERK signalling as the main coupling pathway and show that the two clocks impose daily rhythmicity to the temporal pattern of eclosion by regulating the timing of the very last steps in metamorphosis.

Sexually dimorphic behaviors are fundamental to the biology of many species, including fruit flies and humans. These behaviors are regulated primarily by sex-specific neural circuits or the sex-specific modulation of shared neuronal substrates. In fruit flies, GABAergic neurotransmission plays a critical role in governing sexually dimorphic behaviors such as courtship, copulation, and aggression. This review explores the intricate roles of GABAergic neurons in these behaviors, and focuses on how sex-specific differences in GABAergic circuits contribute to their modulation and execution. By examining these mechanisms in Drosophila, we reveal broader implications for understanding sexual dimorphism in more complex organisms.

The Aedes aegypti mosquito utilizes olfaction during the search for humans to bite. The attraction to human body odor is an innate behavior for this disease-vector mosquito. Many well-studied model species have olfactory systems that conform to a particular organization that is sometimes referred to as the 'one-receptor-to-one-neuron' organization because each sensory neuron expresses only a single type of olfactory receptor that imparts the neuron's chemical selectivity. This sensory architecture has become the canon in the field. This review will focus on the recent finding that the olfactory system of Ae. aegypti has a different organization, with multiple olfactory receptors co-expressed in many of its olfactory sensory neurons. We will discuss the canonical organization and how this differs from the non-canonical organization, examine examples of non-canonical olfactory systems in other species, and discuss the possible roles of receptor co-expression in odor coding in the mosquito and other organisms.

Parasitoid wasps may well be the most species-rich animal group on Earth, and host-parasitoid interactions may thereby be one of the most common types of species interactions. Understanding the major mechanisms underlying diversification in parasitoids should be a high priority, not the least in order to predict consequences from high extinction rates currently observed. The two major hypotheses explaining host-associated diversification are the escape-and-radiate hypothesis and the oscillation hypothesis, where the former assumes that key innovations are major drivers of radiation bursts, whereas the latter rather assumes that diversification depends on processes acting on the standing genetic variation that influences host use. This paper reviews the recent literature on parasitoid speciation in light of these major hypotheses to identify potential key innovations and host use variability underlying diversification. The paper also calls upon recent theoretical advances from a similar system, plant-butterfly interactions, to provide shortcuts in the development of theories explaining the high diversity of parasitoid wasps.

Metamorphosis endowed the insects with properties that enabled them to conquer the Earth. It is a hormonally controlled morphogenetic process that transforms the larva into the adult. Metamorphosis appeared with the origin of wings and flight. The sesquiterpenoid juvenile hormone (JH) suppresses wing morphogenesis and ensures that metamorphosis takes place in the right ontogenetic time. This review explores the origin of insect metamorphosis and the ancestral function of JH. Fossil record shows that the first Paleozoic winged insects had (hemimetabolous) metamorphosis and their larvae were likely aquatic. In the primitive wingless silverfish that lacks metamorphosis JH is essential for late embryogenesis and reproduction. JH production after the embryo dorsal closure promotes hatching and terminal tissue maturation.

Insect herbivore eco-immunology involves complex interactions between herbivore immunity and their natural enemies, and the responses of these interactions to environmental factors including plant anti-herbivore toxins. Plant toxins can affect herbivore immunity, leading to either immunoenhancement or immunosuppression, which in turn influences their vulnerability to parasitoids and pathogens. Herbivore immune responses differ among species regionally, reflecting adaptations to local environmental conditions and natural enemy pressures. Additionally, anthropogenic factors including like climate change, plant domestication, and invasive species are altering these eco-immunological dynamics. Such changes can ripple through food webs, affecting not only herbivores and their natural enemies but also broader community structures. By understanding these complex interactions, we can better predict ecosystem responses to environmental change.

Insects represent the most diverse group of animals in the world. While the olfactory systems of different species share general principles of organization, they also exhibit a wide range of structural and functional diversity. Scientists have gained tremendous insight into olfactory neural development and function, notably in Drosophila, but also in other insect species (see reviews in [1-3]). In the last few years, new evidence has steadily mounted, e.g. the stoichiometry of odorant receptor and co-receptor (OR-Orco) complex. This review aims to highlight the recent progress on four aspects: (1) the structure and function of the OR-Orco complex, (2) chemosensory gene co-expression, (3) diverse neural developmental processes, and (4) the role of genes and neurons in olfactory development and olfactory-mediated behavior.

Amid concerns over chemical pesticide resistance and its associated environmental hazards, parasitoids offer an alternative long-term solution to manage insect pests in agriculture. India's use of parasitoids in pest management has developed in tandem with the rest of the world, and this review summarizes the history of parasitoid-based biocontrol from the past to the present, focusing on problems such as climate adaptability, ecological compatibility, research-based advances, and policy-making. It focuses on successful classical, conservative, and augmentative techniques that form the foundation for implementing effective and sustainable biological control strategies involving parasitoids in India. The components that influence the efficiency of biocontrol activities, such as suitable phenological stages of parasitoids, field deployment techniques, quality assurance, environmental conditions, area-wide approaches, the need for sound habitat management, policy interventions, and public-private partnership are highlighted. Recent advancements in parasitoid mass production, quality control, and understanding competitive ecological interactions have provided prospects for designing effective parasitoid-centered biocontrol programs. The review presents historical breakthroughs in explaining how parasitoids help stabilize the agroecological dynamics that support sustainable food systems, primarily in India.

Insects can adapt quickly and effectively to rapid environmental change and maintain long-term adaptations, but the genetic mechanisms underlying this response are not fully understood. In this review, we summarize studies on the potential impact of chromosomal inversion polymorphisms on insect evolution at different spatial and temporal scales, ranging from long-term evolutionary stability to rapid emergence in response to emerging biotic and abiotic factors. The study of inversions has recently been advanced by comparative, population, and 3D genomics methods. The impact of inversions on insect genome evolution can be profound, including increased gene order rearrangements on sex chromosomes, accumulation of transposable elements, and facilitation of genome divergence. Understanding these processes provides critical insights into the evolutionary mechanisms shaping insect diversity.

Herbivore-induced plant volatiles (HIPVs) are reliable cues that parasitoids can use to locate host patches. Interactions mediated by plant volatile organic compounds (VOCs) are vulnerable to disturbance by predicted climate change and air pollution scenarios. Abiotic stress-induced VOCs may act as false signals to parasitoids. Air pollutants can disrupt signalling by degrading HIPVs at different rates and preventing the perception of olfactory signals by reducing the sensitivity of olfactory receptors or by occluding insect sensillae. As essential components of biological control programmes, efforts should be made to assess how different parasitoid species respond and adapt to HIPVs in predicted scenarios. Since providing parasitoid food sources is a promising practice for boosting biological control, parasitoid-flower interactions deserve attention.