Abstract: 【Aim】 This study aims to investigate the neuropil structures of the brain and the suboesophageal ganglion in larvae of the cotton bollworm, Helicoverpa armigera (Hübner) and to reconstruct their three-dimensional models. 【Methods】 The immunohistochemistry was used to characterize the anatomy of the brain and the suboesophageal ganglion. The laser scanning confocal microscope was used to acquire the confocal image stacks of the brain and the suboesophageal ganglion, which were subjected to image analysis, and the digital three-dimensional reconstructions were created by the AMIRA software. The volumes of the brain and the suboesophageal ganglion and their neuropils were measured by using the statistic tool of AMIRA software and the relative size was analyzed. 【Results】 The larval brain and the suboesophageal ganglion are connected by one pair of circumoesophageal connectives. The brain is composed of protocerebrum, deutocerebrum and tritocerebrum. The protocerebrum contains three prominence neuropils, i.e., optic lobes, mushroom bodies and central body. The other neuropils are lateral, ventral and superior protocerebra, which account for 59.65% of the brain neuropils. Their boundary, however, is hard to discriminate. The deutocerebrum mainly consists of a pair of antennal lobes. The tritocerebrum is located in ventral of the brain and under the antennal lobe. Compared with protocerebrum and deutocerebrum, the volume of tritocerebrum is smaller. The suboesophageal ganglion is also a fusion of three neuromeres, i.e., mandibular neuromere, maxillary neuromere, and labial neuromere from anterior to posterior. Their boundaries are obscure. 【Conclusion】 The neuropils of the brain and the suboesophageal ganglion were presented and their digital three-dimensional models were reconstructed. The models can be rotated and viewed at any angle, thus facilitating the identification of the neuropils and their spatial relationships. The results of this study provide knowledge about basic neuroanatomical principles for understanding the mechanisms underlying information processing, integrating and behavioral regulation.

Key words: Helicoverpa armigera, brain, suboesophageal ganglion, neuropil, three-dimensional model