Larval stages of the holometabolous insect, Tenebrio molitor (Coleoptera : Tenebrionidae) demonstrated the ability to learn a complex maze. The maze consisted of a start box, six blind alleys and a goal box. On the first day of training, the mean number of blind alley errors (BAE) for 10 larval insects was 132.4 (± 21.3 S.D.). This number decreased to 17.1 (± 4.3) after a seven day training period. The mean number of BAE for adult insects previously trained as larvae was 51.6 (±7.8) on day 1, and 7.3 (± 2.4) on day 7. The values for adult controls, which received no larval training, were 90.5 and 11.2, respectively, indicating that adults with previous larval training exhibit a significant improvement in performance as compared to those adults which had no no prior exposure to the maze. This is a clear demonstration for the retention of learning through metamorphosis in this species. This suggests that those brain regions specifically involved in acquisition and memory consolidation (corpora pedunculata and protocerebral bridge of the protocerebrum) do not undergo significant developmental reorganization during pupation. This paper will also discuss neurochemical events associated with various types of learning and localization of brain function in insects and other arthropods. It will be shown that learning experiments and neurochemical analysis can be used to identify specific regions within the central nervous system (CNS) associated with behavioral plasticity in arthropods. The relationship between neurochemical events, learning, memory consolidation and the expression of innate behavior will be discussed. General hypotheses concerning cellular and molecular models of learning will be addressed as well.
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