**1. Introduction**

The development of insect farming is critical for achieving agricultural sustainability goals and dealing with rising food demand, ongoing natural resource depletion, and global climate change. Insects are now being mass-produced as entomophagous arthropods for pest management or for food and feed. During the 1950s and 1960s, the field of insect mass-rearing began with the mass production and release of sterile males for autocidal control of flies such as the screwworm and later with natural enemies during the 1970s, 1980s, and 1990s. By far the sterile insect technique (SIT) is the technique that makes the most use of mass-rearing. Pests are reared in large numbers before being sterilized with ionizing radiation and released into the wild as a viable alternative to chemical pesticides. Male sterile insects compete with male wild insects of the target pest. Females inseminated with sterile sperm are not fertilized and will not give birth. The worldwide directory of SIT facilities (DIR-SIT) indicates that there are more than 142 facilities breeding mainly Diptera, Lepidoptera, and Coleoptera.

The innovation of mass-rearing necessitates the development of artificial diets, as well as a controlled environment with clear and reproducible procedures to achieve the best yields at the lowest costs. For the Mediterranean fruit fly *Ceratitis capitata* (medfly), which is a major key pest that attacks more than 400 hosts, standard rearing procedures were developed by the USDA, IAEA, and the FAO in the 2000s [1]. This document represents the recommendations, reached by consensus of an international group of quality control experts, on the standard procedures for product quality control (QC) that are used now for sterile mass-reared and released tephritid flies. Indeed, despite years of improving the various breeding and release procedures, laboratory sterile males tend to have reduced performance compared to their wild counterparts. Recently microbiome disturbance or dysbiosis has been increasingly recognized as a significant contributor to the poor performance of sterile medfly males, which play a key role in shaping health and fitness. The presence of minor communities such as *Pseudomonas aeruginosa* in the medfly gut at the expense of major communities such as Enterobacteriaceae would result in a decrease in host nutrients and energy metabolic activity in sterile medfly males [2, 3]. Both culture-dependent and culture-independent techniques were used to identify potential dysbiosis after domestication, irradiation, mass-rearing, and handling, highlighting the potential risks to host immunity, development, nutrition, and health. The dominant presence of the enterobacterial community in the medfly's gut contributes to the fly's nitrogen and carbon metabolism, development, and copulatory success [2, 4], as well as its host fitness by acting as a barrier against deleterious bacteria [2]. The dominant species in wild and laboratory medfly populations were identified as *Klebsiella oxytoca* and *Enterobacter agglomerans*, respectively [5].

Even though prevention is preferable to cure, the development of healthenhancing additives such as probiotics began in the 1950s–1980s [6]. Because of their prophylactic efficacy against bacterial infections of the gut and immunomodulating activity, there is agreement on the efficacy of supplementing probiotics to human health conditions [7], poultry [8], and, more recently, aquaculture [9].

With the development of mass-rearing, concern for insects' health increased. Probiotics are already sold to beekeepers to restore the gut microbiota of honey bees following antibiotic treatment. First, anaerobic gut bacteria obtained from bees were studied, along with strains from several additional sources [10]. The most popular probiotic strains for bees are *Lactobacillus* and *Bacillus*, two strains that are associated with honey bees and/or have been chosen from the bee environment [11]. Over the past decade, experimental supplementation of probiotics to the medfly diet has provided key insights. Probiotics stimulate production and modulate the immune system. To what extent are these probiotics thought to be a preventative measure for medfly mass-rearing? This chapter describes ongoing research in this field and attempts to analyze how probiotics might aid sterile medflies in fighting diseases, dealing with pesticides, and dealing with the effects of climate change.

*Probiotics as a Beneficial Modulator of Gut Microbiota and Environmental Stress… DOI: http://dx.doi.org/10.5772/intechopen.110126*
