

Si (ME SOI 111 I\DIA\ INSEC rS, 



|( HAP. VI. 



HiLIOTHjHSM 



- 



.( cw. • 



• ■ - 



ANEMOTR.-'TISM 

 .. A„ Cv... ts ) 



- 



■I 



"1 



THIGMoTROFH 



f Cenf.cT Ml> S,U S ) 



RM £OTRoPlSM 



■ •■ w«r„ . c>. ...• 

 Diagram ihowing fropic Reactions 





as heliotropic reactions are not necessarily the same as phototropii 

 and the two may indeed be opposed to one another. A moth which 

 hides away from daylight (negatively heliotropic) is strongly at- 

 tracted by artificial light at night, and that this positive phototro- 

 pism is not entirely due to the fact that it only occurs during 

 the insect's normal hours of activity is shown by the fad thai this 

 reai tion is exhibited must strongly on dark nights. It is a fact of 

 common observation that very few insects fly in to light on bright 

 moonlight nights. The use of light-traps to capture insects and 

 control crop-pests is a practical application of this reaction, as is 

 also the capture of fish at night by the aid of torches. The Bedbug 

 may be cited as an example of an insect exhibiting strong negative 

 phototropic tendencies. 



Heliotropism has been studied especially in the case oi many 

 butterflies which may be observed to settle and then carefully to 

 orienl themselves to the sun's rays so that they may obtain in some- 

 cases a maximum of heat-rays on their wings or in other cases so 

 that a minimum amount of shadow may be thrown by the wings. 

 Animals which are positively heliotropic have been called phane- 

 I and those which avoid the light of day ervptozoic. 



Ch( motropism, it must be admitted, is a vague and elastic term 

 covering responses to such stimuli as those of smell equally with 



