## 1 Introduction  
_Dendroctonus_ bark beetles (Curculionidae: Scolytinae) are key ecological agents of coniferous forests, and some of their species are the most destructive pests in these communities in North and Central America [1; 2]. These bark beetles complete their life cycles under the bark of host trees, except for a brief dispersal period during which adults find a new host and mate. These insects locate and colonize their host trees through the detection of specific blends of terpenoid compounds (kairomones)produced by the trees, as well as aggregation and antiaggregation pheromones [3; 4]. Aggregation pheromones are essential either as sex attractants or as coordinators of massive attacks against the hosts, whereas antiaggregation pheromones regulate the population of conspecifics that can settle on the trees [5]. Pheromone production in bark beetles, including the _Dendroctous_ species, is an adaptive strategy favored by natural selection because pheromones provide information about food availability and sources, conspecific attraction, reproductive partners, and regulation of population density [6]. In these insects, pheromone production has several ecological sources, such as microbial assisted synthesis [7], autoxidation of host compounds [8], sequestration and release of host compounds [9], transformation of host terpenes to pheromonal compounds [10], and endogenous production [4; 11; 12; 13; 14; 15]. Pheromone production can vary based on insect health, mating system, colonization strategy, species aggressiveness, and geographical region [16; 17; 18; 19]. The mevalonate (MVA) pathway is an endogenous metabolic route present in eukaryotes, archaea, and some eubacteria. This route is directly involved in the synthesis of cholesterol, hormones, and other isoprenoids metabolites [20; 21; 22]. Hemi- and monoisoprenoids compounds, as well as bicyclic acetals used as aggregation or antiaggregation pheromones by bark beetles, are produced through de novo synthesis in the gut of these insects [4; 23; 24; 25; 26; 27; 28]. Although it is not known how the MVA pathway is regulated in bark beetles, it has been demonstrated that feeding on phloem triggers the synthesis of Juvenile Hormone III (JH III) in the corpora allata [29], thereby regulating transcription of the genes coding for the enzymes that catalyze the synthesis of terpenoid backbones (_AACT_, acetoacetyl-CoA thiolase; _HMGS_, 3-hydroxy-3-methylglutaryl-CoA synthase; _HMGR_, 3-hydroxy-3-methylglutaryl-CoA reductase; _MK_, mevalonate kinase; _PMK_, phosphomevalonate kinase; _MDPC_, diphosphonate decarboxylaseise; _IPPI_, isopentenyl diphosphate isomerase; _GPPS_, geranyl diphosphate synthase; _FPPS_, farnesyl diphosphate synthase; _GGPPS_, geranylgeranyl diphosphate synthase) [30; 31]. Most of these enzymes synthesize a unique product, except for GPPS and FPPS, which can be mono- or bifunctional (GPPS/FPPS) [32], as reported in _Pluedon cochleariae_[33], _Manduca sexta_[34], _Myzus persicae_[35], and _Dendroctous ponderosae_[36]. _Dendroctous rhizphag_ [PERSON] is an endemic species of the Sierra Madre Occidental in Mexico and an atypical species within the _Dendroctous_ genus because generally just one or two pairs, rather than tens to thousands of pairs, colonize and kill a single host of seedlings or saplings <3.0 m high and <20 cm in diameter of 11 pine species (Pinales, Pinaceae), mainly _Pinus arizona_ [PERSON], _P. engelmannii_ [PERSON], _P. leiophylla_ [PERSON] and [PERSON], and _P. durangensis_ [PERSON] [37; 38]. The life cycle of this bark beetle is univoltine and synchronous. Females lay their eggs in groups, and when larvae hatch, they feed gregariously on the phloem of the tree stem. During winter, larvae remain in the roots to survive the low temperatures, and in early spring, they regroup in the primary roots to transform into pupae and adults. Females and males emerge in the early summer to colonize a new host and mate [39]. Chemical ecology studies in _D.