holometabolous insects, such as the noctuid moth Agrotis ipsilon 58 , as well as several beetle species 59 including the red flour beetle Tribolium castaneum 60. T. castaneum is a member of the largest insect order (Coleoptera) 61,62 and a major pest of stored cereal products 61,63,64. With its annotated genome sequence 26,65-67 , an expanding genetic toolbox 68-70 including strong systemic RNA interference (RNAi) 71-73 , and its relative longevity of up to two years 74 , T. castaneum represents an eligible beetle model for studying adult plasticity. We concentrated on olfaction which is supposed to be a main input into the mushroom bodies of T. castaneum 26 , to answer whether the adult persisting neurogenesis is genetically predetermined and continuation of developmental processes or if it is activity-dependent. Results Identification of newly born cells. To label adult-born cells, we used the 5-ethynyl-2′-desoxyuridine (EdU) method 75,76. With this method, we reliably and exclusively labelled the mushroom body neuroblasts and their progeny, while neurogenesis is not present in other areas of the cerebral ganglion of the red flour beetle (Fig. 1A). The neuroblasts were distinguished from their progeny based on their larger size (Fig. 1B). We confirmed that in T. castaneum, adult-born Kenyon cells usually derive from two neuroblasts (NB) per hemisphere and send their axons into the core of the mushroom body peduncle (PED) and lobes as shown by Zhao and colleagues 60 (Fig. 1C). The neuronal identity of the EdU labelled cells was verified by demonstrating co-localization with the reporter signal (Fig. 1D-D") in the neuron labelling EF1-B-DsRed line 77 , as well as immunohistochemical staining against the glia cell marker reversed polarity 78 resulting in no co-localization (Fig. 1E-E").