## 1 Introduction
Until now, most research on the reproductive physiology of insects has focused on the role of these JH pathway components in females, while their exact role in males is much less understood. Therefore, in the current study we decided to focus on the role of the JH receptor components Met and Tai in the reproductive maturation of males of the desert locust, _Schistocera gregaria_. Maturation in crowd-reared adult male _S. gregaria_ is associated with the display of sexual behavior and the bright yellow coloration of the cuticle due to the accumulation of carotenoids [33; 34]. The role of JH in male locusts has previously been studied by allatectomy (physical removal of the CA or chemical apoptosis of the CA cells using precocene) and JH (analog) treatments [35; 36]. In this regard, [PERSON] published an interesting study showing that JH can rescue the yellow coloration of the cuticle, as well as the production of maturation pheromone emissions, in allatotectomized male _S. gregaria_[37]. Phenylacetonitrile (PAN) later turned out to be a critical volatile in the pheromone bouquet of sexually mature gregarious male desert locusts [38; 39; 40]. PAN acts as a courtship inhibiting pheromone with which sexually mature males can ensure postcopulatory mate guarding [41]. Although JH levels correlate well with PAN production in adult males, JH is suggested to regulate PAN biosynthesis only indirectly by stimulating the development of pheromone producing tissues [42; 43]. Furthermore, a study by [PERSON] and [PERSON] has shown that JH is necessary for the growth of the male accessory glands (AG) and for the associated protein synthesis in the fat body [44]. The insect fat body plays a pivotal role in many metabolic processes, including nutrient and energy homeostasis,as well as reproduction [45]. A clear correlation between the JH biosynthetic activity of the CA and the dry weight of the AG was also found in a study by [PERSON] and [PERSON], who additionally showed a direct relationship between rates of JH release from the CA and the age of the animals [46]. In the migratory grasshopper, _Melanoplus sanguinipes_, the biosynthesis of specific proteins in the AG is similarly highly dependent on JH [47]. Adequate nutrient uptake and allocation are pivotal for successful reproductive development in insects [48]. In general, the insulin/insulin-like growth factor (IGF) signaling pathway (ISP), sensing the organism's nutrient status and positively controlling vitellogenesis and oocyte growth in female insects, plays a crucial role in the trade-off between reproduction and longevity. Different studies have highlighted the complex interplay between JH and ISP in female reproductive physiology [49; 50]. Our previous studies in adult female desert locusts also illustrated this interplay. RNAi-mediated knockdown of _Scg-Met_ resulted in a significant increase in relative transcript levels of two neuroparasins (_Scg-NP3_ and _Scg-NP4_) in the fat body, while _Scg-IRP_ (insulin-related peptide) transcript levels decreased, suggesting a consistent cross-talk between JH signaling via _Scg-_Met and _Scg-_NP and _Scg-_IRP expression [14]. In line with this, knockdown of _Scg-_IRP in female S. _gregaria_ was shown to reduce vitellogenin (_Vg_) transcript levels and oocyte growth [51]. This study also showed that knocking down the _S. gregaria_ NPs, in contrast to _Scg-_IRP, increased _Scg-Vg_ transcript levels and resulted in larger oocytes. NPs were initially characterized as antigonadotropic factors from the _pars intercerebralis-corpora cardiaca_ (CC) neurohemal complex of locusts [52; 53; 54]. They belong to a large family of cysteine-rich secreted proteins, which also includes the ovary ecdysteroidogenic hormone (OEH), a gonadotropin factor in blood-fed mosquitoes, and shows sequence similarities with the most conserved region of vertebrate insulin-like growth factor binding proteins (IGFBPs) [55; 56; 57].