THE FISHES, MOLLUSCA, AND OTHER OBJECTS. 29 



Fig. 17. 



The males are well known for their pugnacity, and 

 for the beautiful colours of scarlet and green they 



put on in the spring, at the 



time when they make their 

 aquatic nests. For, strange to 

 say, this and one or two others 

 are genuine nest builders ! 

 Towards the middle of April 

 they may be observed (if kept 

 in a fresh-water aquarium), 

 collecting small pieces of stick 

 and wet moss, so saturated 

 that they cannot float. A pile 

 of these is made, with a hole 

 on the top. The stickle- 

 backs then collect, with their 

 mouths, fine sand, and trickle 

 it all round the little cone. 

 Woe be to any invader of this 

 little nest, after it has been 

 formed, and the female has 

 deposited her ova therein ! 

 Small as the three-spined 

 stickleback is indeed, per- 

 haps, the smallest of all our 

 British species it does not 

 hesitate to attack much larger 

 individuals, and will even tilt 



at the Stick you point towards 



the little nest it is guarding ! The ova hatch in 



