PREY CAPTURE IN MANTIDS 



55 



Normally flies sitting on the right side are missed to the left and vice 

 versa. I shall discuss these results later. 



Next the head was given a fixed position relative to the prothorax by 

 what may be called a little bridge of balsa wood fastened on both ends with 

 paraffin, so that the neck region was not touched at all. Fig. 3 shows the 

 effect of a head deviation of 10 to 30 degrees to the left (in 6 animals). 



x>~_. 



right tendency 



faults 



275 strokesj yalue 



1 Z 3 I. 5 6 7 



Time (days) 



Fig. 3. Result of head fixation 10 to 30° to the left (6 individuals). Ordinate: 

 frequency of misses (solid circles) and right tendency (open circles), respectively. 

 Abscissa: days after fixation; the performance recorded before head fastenmg i_s 

 shown left from 0-line. The limits of expectation, each based on a P-level of 0.025, 

 are plotted in two of the values. 



There is a large bias to the right now and a frequency of misses of about 

 75%, remaining constant for at least a week. There may be a slight im- 

 provement of about 10% the following week, but in general we get another 

 proof of the small learning capacity of the mantid. If the head is fastened 

 near its normal median position the animal has a smaller bias and a better 

 achievement. In some cases where the exact median position was reached 

 by chance, the bias was zero and the frequency of misses normal. 



In the next set, head fastening and deafferentation were combined. The 

 result just presented was obtained even in individuals which had under- 

 gone total proprioceptive deafferentation, suggesting that the effect of the 

 operation is cancelled if the head is fixed. In order to get a more rigorous 

 proof of this, the proprioceptors were eliminated on one side only. For in 

 the controls, without head fastening, this intervention causes not only a 



