112 ANIMAL COLORATION. 



two coloured plates the colour variations of Thomisus onustus 

 a species abundant in the south of France. This spider 

 frequents the flowers of Convolvulus arvensis, and is so- 

 abundant during the months of August and September that 

 nearly every plant has its spider ; it is evident, therefore, that, 

 in spite of the numerous insect visitors to these flowers, there 

 must be a certain amount of competition for food among the 

 spiders ; this is especially the case if it be true that the spider 

 limits itself almost exclusively to two Diptera, ignoring the 

 other insects. The flowers of this convolvulus show three 

 varieties : one is pure white ; another pink, with traces of a 

 vinous red externally ; while the third is a paler pink tinged 

 with green externally. These three varieties of the convolvulus 

 are inhabited by three varieties of the Thomisus, which corre- 

 spond exactly in their hues with the flower, with the exception 

 of the one which lives in the white flowers ; this variety of 

 spider has a blue cross on the abdomen, and the extremities of 

 its legs are likewise bluish. Blue, however, may be suggestive 

 of shadow, and not render the animal very conspicuous. These 

 three varieties do not embrace all the colour modifications 

 of which the spider is susceptible ; it becomes a dark red 

 when upon the flowers of Dahlia versicolor, which has a similar 

 colour, and yellow when upon the flowers of the yellow 

 Antirrhinum majus. 



The term " variety " has been made use of in referring to 

 these spiders ; but the use of the term is misleading in so far 

 as it implies a fixed colour form, for Prof. Heckel found that 

 the spiders were capable of changing their colour when trans- 

 ferred from one flower to another, but that the change took 

 three or four days for its accomplishment. 



It is only just to mention that the experiments, as described, 

 were not absolutely conclusive. Three spiders were taken 



