BIOLOGY 

 LIBRARY 



A CONTRIBUTION TO THE KNOWLEDGE OF THE 

 INTERNAL ANATOMY OF TRICHOPTERA.* 



By HAZEL ELISABETH BRANCH, 

 Wichita, Kansas. 



NERVOUS SYSTEM. f 



The nervous system of the trichopterous larvas is comparatively 

 primitive and agrees with that of the lepidopterous larvas in the number 

 of pairs of ganglia and also resembles, in some respects, the arrangement 

 in relation to the body segments. Exclusive of the ganglia in the head, 

 which are normal in number and position, there are three pairs for the 

 thorax and eight pairs for the nine abdominal segments, the seventh 

 abdominal segment being the most posterior in which ganglia are found. 



In the head of Limnophilus indimsus the supra-cesophageal ganglia 

 are situated with their anterior margin on a line immediately posterior 

 to the eyes. The combined width of the ganglia is about one-half that 

 of the head. Each ganglion gives off laterally and in a forward direc- 

 tion, an optic nerve which branches to supply each of the simple eyes 

 of the visual area. In front of the junction of the two ganglia is the 

 frontal ganglion, small and shield shaped, connected to the supra- 

 cesophageal ganglia by a pair of arms. Proceeding from each arm of the 

 frontal ganglion, close to its attachment with the supra-cesophageal 

 ganglion, is a nerve which extends forward and sends an outer branch to 

 the labrum, and an inner branch to the dorsal region of the buccal 

 cavity, see Plate XIV, Figs. 4 and 5, at lb x and b. Between the point 

 of attachment of the arm of the frontal ganglion with the supra-cesoph- 

 ageal ganglion, and the optic lobe, (opt), is the slender antennal nerve 

 rising from the anterior margin of the ganglion and possessing a fellow 

 in like position upon the other ganglion, see Plate XIV, Figs. 4 and 5 

 at ant. Upon its posterior face, each ganglion gives rise to a pro- 

 tuberance from which issues a nerve that converges toward its fellow 

 and meets it upon a median line. At this union a small 

 ganglion is formed and to this are also joined, the nerves 

 coming from the sympathetic ganglia. These sympathetic ganglia are 

 single, one upon each side of the oesophagus and possessing a nerve 

 connection with the posterior protuberance of the supra-cesophageal 

 ganglion of its respective side, See Plate XIV, Figs. 4 and 5. 



The recurrent nerve of the frontal ganglion extends in a posterior 

 direction between the supra-cesophageal ganglia and the oesophagus 



* A contribution from the Department of Entomology, Cornell University, 

 prepared under the supervision of Dr. O. A. Johannsen, to whom and also to Dr. 

 J. G. Needham and Dr. J. T. Lloyd, I wish to express my gratitude for the valuable 

 assistance rendered. 



t In gross dissection, hot water killing and Gilson's fixing solution were found 

 to be most advantageous. 



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