Developmental anatomy of the central nervous system of the cotton leaf worm, spodoptera littoralis boisd.
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The central nervous system, C. N. S., of the cotton leaf worm, Spodoptera littoralis (B.) develops from a median row of embryonic neuroblasts which divide repeatedly to form a double ganglionic chain. The two chains fuse together laterally giving rise to the larval C.N.S. which is differentiated into a brain, a frontal, a suboesophageal, three thoracic and seven abdominal ganglia. During the pupation period, the larval C.N.S. undergoes marked changes leading to the formation of the C.N.S. of adult moths. These changes involve fusion of certain parts of the system and degeneration of others. The brain and suboesophageal ganglion fuse together forming a large brain mass which is pierced by the oesophageal passage. The first thoracic ganglion remains unchanged. The second and third thoracic ganglia, as well as the first abdominal ganglion, also fuse together producing the large second thoracic ganglion of adult moths. The fifth and sixth abdominal ganglia are completely degenerated. Thus, the fully-developed C.N.S. of adult moths consists of a brain, a frontal, two thoracic and four abdominal ganglia.