THE BEHAVIOR OF A PARASITIC COPEPOD 51 



VIII. REACTIONS TO HEAT 



Loeb (1893), while experimenting with the copepod Temora 

 longicornis, found that increasing the temperature of the water 

 caused positively phototropic individuals to become negative, 

 and vice versa ; decreasing the temperature of the water brought 

 about a change in normally negative individuals and caused 

 them to become positive. Holmes (1901), found that increas- 

 ing the temperature hastens, or may even induce, positive 

 reactions among certain amphipods. This same author (1905), 

 also found that an increase in temperature caused Ranatra to 

 accentuate its positive phototaxis, while a decrease tended to 

 produce the negative reaction. Yerkes (1900), could not induce 

 any changes in the behavior of Daphnia and Cypris to light by 

 varying the temperature. Parker (1901), also met with no suc- 

 cess when he tried to induce changes in the light reactions of 

 Labidocera by similar methods. 



In the present experiments with heat, it was found that in- 

 creasing the temperature of the water caused no change in the 

 light reaction of Lernaeopoda. Six copepods were placed in an 

 oblong dish of water, whose temperature was 5 8° F. These 

 were then attracted to one end of the receptacle by a 60 c. p. 

 Mazda lamp. At the opposite end, water that had been heated 

 to near the boiling point was slowly poured at intervals a few 

 minutes apart. As soon as the warmer water reached the ani- 

 mals they became very active, darting about rapidly; but none 

 of them left the illumined side of the dish. As more hot water 

 was supplied, the movements became slower, until at the tem- 

 perature of 81 ° F. all of them were dead in the region of posi- 

 tive phototaxis. It was thus seen that increasing the tempera- 

 ture does not alter the behavior of the copepods to light. 



IX. REACTIONS TO CHEMICALS 



The effect of chemicals was next tried, with two purposes in 

 view:, first, to determine whether chemicals could reverse the 

 behavior of the copepods to light, and second, to find out the 

 solution of the chemical necessary to kill the parasitic organism 

 while in this free-swimming stage of its existence. Only the 

 first of these problems will be discussed here. The other will 

 be dealt with in another paper on the economic aspects of 

 Lernaeopoda edwardsii. 



