3 o8 ANIMAL DEFENCES 



regards adult Butterflies and Moths, colours and markings of the 

 kind may either be genuine warnings or belong to the category 

 of spurious warnings, which will be described in the sequel. 



Certain unpalatable Beetles exhibit warning colours, and of 

 these good examples are afforded by the various species of Lady- 

 bird (Coccinella), which exhibit red spots on a dark ground. 



Warning Coloitrs of Arachnida. The colours of this group 

 have not been studied in the same detail as those of Insects, and 

 perhaps the best-known case of warning is that afforded by a 

 black-and-red Australian Spider (Latrodectus scelid), which has 

 already been described (p. 127). 



Warning Colours of Lower Invertebrates. There can be no 

 doubt that the bright hues of many marine Bristle-Worms have 

 a w r arning significance, though we have, at present, but little 

 evidence on the subject. There is, however, at least one clear 

 case, i.e. Poly cirrus aurantiacus, a bright-red worm with very 

 numerous long tentacles of an orange colour, which has been 

 the subject of investigation by Garstang. This animal belongs 

 to a family (Terebellidte) of tube-inhabiting worms, but has given 

 up this mode of life, and is found crawling on stones and sea-weed 

 in pursuit of food. When alarmed it coils itself up so as to be 

 surrounded by its tentacles, and it was shown that these are very 

 distasteful even to voracious sorts of fish. It is an interesting fact 

 that when irritated these tentacles gleam with a phosphorescent 

 light, and this no doubt serves as a warning to the numerous fishes 

 which are in the habit of feeding by night. It would be unsafe, 

 however, to conclude from this and similar cases that the wide- 

 spread phenomenon of phosphorescence always has a warning 

 significance. It no doubt, just like colour, serves various ends 

 (see p. 86), though it cannot be said that its function is well 

 understood in a large number of cases. 



Among unsegmented worms it is probable that some of the 

 brightly- coloured conspicuous Planarians, which do not attempt 

 to conceal themselves, possess noxious properties, and Gamble 

 (in The Cambridge Natural History] suggests that this may be 

 the case with two large Mediterranean forms, of which one 

 (Pseudoceros velutinus) is jet-black, and the other (Yungia 

 aurantiaca) bright-orange in hue. 



Sea -Anemones and Coral -Animals are often of the most 

 brilliant colours, and these may well be of warning nature, for 



