In insects, the nervous system is generated by neural stem cells (neuroblasts), which arise from the neuroepithelium. In the part of the neuroepithelium which gives rise to the ventral nerve chord (thoracic and abdominal ganglia), the arrangement of individual neuroblasts has been compared in several different insect species (Biffar and Stollewerk, 2015). The red-flour beetle has some signaling molecules in the nervous system called neuropeptides, these molecules affect a broad range of biological processes, including development, metabolism, behavior, and reproduction. The peptides and protein hormones produced in endocrine cells or neurons as larger precursors (Li et al., 2008). These molecules are usually considered acting as neuromodulators and transmitters that modify the effect of “classical” transmitters at the synapse (Binzer et al., 2014). The enzyme acetylcholinesterase (AchE) is essential in all animals due to its importance in synapses of cholinergic neurons in the central and peripheral nervous system. There are two AchE genes, which have been widely studied due to their role in resistance to insecticides (Lu et al., 2012). In addition to the neuropeptides, biogenic amines are physiologically neuroactive substances that affect behavioral and physiological traits in invertebrate and vertebrate animals, and they act as neurotransmitters, neuromodulators, and neurohormone in the central and peripheral nervous systems. Many behaviors in arthropods are controlled by neuroactive substances or biogenic amines, including octopamine, dopamine, and serotonin that are derived from the amino acids tyrosine or tryptophan. When insects are attacked by natural enemies, they often freeze. This behavior is known as tonic immobility; it is also called death-feigning or playing possum (Nishi et al., 2010).
Within the processes controlled by the nervous system is a sense of smell, hearing, and tactile perception. Insects possess sensory structures called antennas that allow you to perform these processes and are crucial to the ability of the beetle to interact with their environment (Angelini et al., 2009). The olfactory process begins with the passage of odorants from the periphery to odorant receptors by chemosensory proteins (CSP) or odorant binding proteins (OBPs) through the lymph, followed by detection via odorant, ionotropic similar to glutamate or gustatory receptors. The insects have olfactory sensilla, which are hair-like structures with the highest density on the antennae. They are housing the dendrites of the odorant receptor neurons and are filled with aqueous lymph (Dippel et al., 2014). Olfactory information is likely to represent one of the most dominant sensory inputs in T. castaneum. This is reflected in its large number of odorant receptor genes and the general neuroanatomical makeup of the insect brain (Binzer, et al., 2014).