238 



COLLEGE ZOOLOGY 



( autonomic ) nervous system which controls 

 the "involuntary" movements of the diges- 

 tive tract, heart, aorta, and reproductive 

 system. 



Supraesophageal ganglion 

 (brain) 



SeTise organs. Grasshoppers possess or- 

 gans of sight, hearing, touch, taste, and 

 smell. The compound eye and ocellus (Fig. 

 132) have already been noted. Vision by 



Optic lobe 

 Connective 

 Subesophageal ganglion 



Nerve cord 

 —Abdominal ganglion 



Figure 138. The grasshopper nervous system in dorsal view. (Redrawn from Principles of 

 Insect Morphology, by R.E. Snodgrass. Copyright 1935 by McGraw-Hill Book Co., Inc.) 



means of the compound eyes has been de- 

 scribed in the crayfish. The ocelli are thought 

 to be primarily organs of light perception, 

 although it is possible that they may form 

 crude images at close range. The pair of 

 auditory organs are located on the sides of 

 the tergite of the first abdominal segment. 

 Each consists of a tympanic membrane 

 (tympanum) stretched with an almost cir- 

 cular sclerotized ring; sound vibrations in 

 the air set the tympanic membrane in mo- 

 tion, and this in turn affects a slender point 

 beneath the membrane which is connected 

 to sensory nerve fibers. Some of the insects 

 hear sounds beyond the range of the human 

 ear. Sound is produced by grasshoppers by 

 rubbing the tibia of the hindleg with its 

 rough surface against a wing vein which 

 causes it to vibrate. The antennae are sup- 

 plied with the principal organs of smell. 

 Organs of taste are located on the mouth 

 parts. The hairlike organs of touch are 

 present on various parts of the body but 

 particularly on the antennae. 



Reproductive system 



Female grasshoppers can easily be dis- 

 tinguished from males because of the pres- 



ence of the ovipositor (Fig. 136). In the 

 female there are two ovaries. Each consists 

 of several tapering egg tubules called 

 ovarioles, which, however, do not possess a 

 lumen (Fig. 139). The ovarioles contain 

 oogonia and oocytes arranged in a linear 

 series, nurse cells, and other tissue cells. The 

 oocytes grow as they proceed posteriorly 

 down the ovariole, hence the ovariole be- 

 comes gradually larger toward the posterior 

 end. The ovarioles of each ovary are at- 

 tached posteriorly to an oviduct into which 

 the eggs are discharged. The two oviducts 

 unite to form a short vagina which leads to 

 the genital opening between the plates of 

 the ovipositor. A tubular seminal receptacle 

 ( spermatheca ) , which connects with the 

 dorsal wall of the vagina, receives the 

 spermatozoa during copulation and releases 

 them when the eggs are fertilized. 



In the male are two testes in which 

 spermatozoa develop (Fig. 139). These are 

 discharged into a vas deferens. The two 

 vasa deferentia unite to form an ejaculatory 

 duct which runs through the penis, at the 

 end of which is the sperm-escape opening. 

 Accessory glands are present at the anterior 

 end of the ejaculatory duct. 



