Preface

Diptera, also called true flies, are soft-bodied, delicate, and usually small-sized insects. They comprise one of the major insect orders with rich species diversity. To date, more than 152,000 species of flies have been described within more than 188 recognized families. It is estimated that more than 1,000,000 species probably exist today that need to be explored and recognized.

Diptera are abundant throughout the world. They are reported to be prevalent in the tropics and sub-Arctic regions, at sea level, on beaches, and even on mountains. Only the cold Arctic and Antarctic ice caps are without these flies. Because of their ubiquitous presence in diverse habitats, dipteran flies are of considerable economic importance. They play a valuable and varied role in the ecosystem and human life. These tiny organisms are widely known for their role as model research organisms, ecological indicators, scavengers, pollinators, food for predators, and control agents of insect pests such as parasitoids and predators. The pestiferous groups can, however, also transmit serious ailments to humans and animals, and can significantly affect agriculture and forestry.

This book highlights advances in dipteran biology, their development, pest status and management. Conventional management strategies using chemical and biorational products, their bio-efficacy, and mode of action are covered, along with innovative and advanced control interventions in the form of mechanical devices, physiological disruptors, and those acting at biochemical and molecular levels.

The five chapters, arranged in three sections, each cover a different and novel aspect of the field of diptera. Section 1, 'Physiology of Diapause in Dipterans', covers research progress on the diapause of dipteran insects, a physiological process that enables them to survive in a natural environment otherwise unconducive to their survival. The phenomenon provides an adaptive advantage for flies, ensuring that their life cycle is synchronized for optimal growth, development, and reproduction. Diapause is categorized according to the requirement, the development stages of flies, and the steps in the process. Chapter 1 also elaborates on the environmental signals inducing and regulating diapause onset, sensitive insect states of diapause conditions, the endogenous molecular mechanism of diapause, and previous research results. The diapause process and intrinsic mechanisms in dipteran insects are analyzed in terms of endogenous changes in hormones, metabolism, genes and proteins, etc.

Chapters 2 and 3 under Section 2, 'Conventional and Advanced Strategies for Mosquito Management', focus on mosquitoes, the medically significant dipterans responsible for transmitting a number of serious diseases including dengue, Chikungunya and Zika viruses, malaria, encephalitis, filariasis and yellow fever. Chapter 2 illustrates the biology and diversity of the three main mosquito genera, *Anopheles, Aedes,* and *Culex*. Several traditional measures are discussed, such as use of biological agents – larvivorous fishes and crustaceans – and the application of chemical and plant-based toxicants in the larval habitat. Physical and behavioral processes, such as the frequent use of mosquito nets, repellents derived from plants, electrical traps and attractant traps in mosquito management, are described at length along with challenges in the implementation of these initiatives.

Chapter 3 discusses advances in mosquito control interventions devised to induce genetic, physical and behavioral modifications in mosquitoes. Strategies examined range from the sterile insect technique (SIT) inducing male sterility to reduce vector population, developing flightless females by the release of insects carrying a dominant lethal (RIDL), creating transgenics with abnormal and lethal genes, using gene drive technology to genetically modify mosquitoes and reduce their transmission competency, reducing the vectorial capacity by *Wolbachia* infection, and attracting and killing mosquitoes *via* application of attractive toxic sugar baits (ATSB). The use of lasers and light detectors to investigate mosquitoes' behavior, and enhance their trap and kill through high-power lasers are also described.

Section 3 is titled 'Biology and Management of Dipteran Pests'. Chapter 4 discusses dipteran pests that damage different parts of garlic and onion plants and cause extensive crop losses. The biology, life cycle, and pest status of the two most significant dipterans, *Delia platura* and *Delia antiqua,* are described, with cultural, biological and chemical control interventions for integrated management of these pests. The importance and management of minor pests such as leaf miners are also discussed.

Chapter 5 discusses the most significant walnut pest, the walnut husk fly (*Rhagoletis completa* Cresson), which causes crop losses of up to 80% in many growing regions, including the United States and Europe. The chapter describes the geographic distribution of this pest, its bionomics and infestation symptoms, and its effect on yield quantity and quality. New and traditional monitoring and control methods are reviewed; biotic protection and the possible role of phenolic compounds in cultivar resistance to walnut husk flies are emphasized.

I hope that this book will serve as a useful handbook for students, researchers and practitioners associated with the field of insects, and that the potential research directions it indicates will inspire future research ideas.

> **Sarita Kumar** Department of Zoology, Acharya Narendra Dev College, New Delhi, India

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Section 1

Physiology of Diapause

in Dipterans

## Section 1
