NEURO-ENDOCRINE SYSTEMS OF IN VETITE3RATES 451 



oothecal chamber for the period of embryonic development, the maturation 

 of additional eggs must be suppressed. An important step in the maturation 

 of insect eggs is the deposition of the yolk. The incorporation of yolk is 

 promoted by a hormone secreted by the corpora allata, a pair of organs in 

 the head (see Scharrer, 1946). The control of the corpora allata has been 

 studied in a number of Orthoptera. 



In the roach Leucophaea, for example, Engelmann and LUscher (1956) and 

 Engelmann (1957) showed that the corpora allata have two distinct innerva- 

 tions: from the subesophageal ganghon and from the protocerebrum of the 

 brain. When a female roach is carrying fertilized eggs, the corpora allata 

 show no sign of secretion. If the nerves from the brain to the corpora allata 

 are severed, the glands secrete, the ovaries become active, and yolk is deposited. 

 If the nerves from the subesophageal ganghon are severed along with the 

 nerves from the brain, the corpora allata do not secrete. Apparently the 

 corpora allata have a dual innervation: excitatory from the subesophageal 

 ganglion and inhibitory from the brain. 



The inhibition of the corpora allata does not seem to involve the neuro- 

 secretory cells of the brain, whose axons run in the nerves going from the 

 brain to the corpora allata, because inhibition is eliminated by destroying a 

 part of the protocerebrum of the brain that does not contain neurosecretory 

 cells. 



When the female Leucophaea gives birth, egg development begins once 

 again. This shows that the corpora allata have been released from inhibition. 

 Engelmann showed that the inhibitory center of the protocerebrum is stimu- 

 lated by a chemical released by the de\el ^ping cgg^. The control system in 

 Leucophaea is diagrammed as Fig. 3. 



Similar control systems are found in other \ i\ iparous roaches. The principal 

 variation from species to species is in the way in which the inhibitory center is 

 regulated. In BJatella gernianica and in Pycnoscelus surinamensis, Roth and 

 Stay (1959) showed that the developing eggs in the oothecal chamber or 

 uterus stimulate sensory receptors. The sensory messages ascend the ventral 

 nerve cord and stimulate the inhibitory center in the brain. Consequently, 

 during the development of the embryos, secretion by the corpora allata is 

 suppressed. 



The roach, Diploptera punctata, shows a variation on the same theme. In 

 this species. Engelmann (1959) showed that the CDrp^ra allata of the aiult 

 female are inhibited as bng as the an'md remains a virgin. Ori';e the TeTialcs 

 are mated, the glands secrete an J yjlk iep )siti3n b^gii-.. Ti; 'Zivi )V\ alhti 

 can also be activated by arti.lcial mating w;t'i a ghs^ "sp::.nU )p'i)r:*\ T le 

 mechanical stimuh of mating seem tj prjviJe a signal w!iich inhibits aeti'.ity 

 in the corpora allata inhibitory center of the brain (see Fig. 4). Therefor;, this 

 control system rehes on the inhibition of an inhibitory nerve supply. 



Once the development of the eggs has started in Diploptjra, the cycle 



