14 
under-lip provided with a formidable pair of jaws, carefully 
concealed when not in use, whilst the adult when flying about, 
seems to kill butterflies, etc., merely for the sake of killing. 
Male and female water beetles, the larvae of gnats and 
mosquitoes were also shown, and with the last the lecturer drew 
attention to the breathing apparatus which necessitated their 
rising to the surface of the water, hence medical men strongly 
advocated pouring paraffin oil on stagnant pools in districts 
infected with malaria or yellow fever, since the poison giving rise 
to these terrible diseases is now known to be conveyed entirely 
by certain species of mosquitoes, and the layer of paraffin would 
prevent the larvze protruding their breathing apparatus above the 
water, and so they would perish. 
Attention was then directed to the water spider and his 
ingenious diving bell. First a globe of water-proof silk is spun at 
the bottom of the pond, and then, by periodic visits to the surface 
of the water, small air bubbles are collected around the spider’s 
body and introduced into the silk bell so as to make it habitable. 
Finally, a slide was shown anda description given of the 
stickleback’s little nest. The female is with difficulty enticed into 
the nest, and having laid her batch of eggs, she secretly departs 
and leaves the work of tending the nest to her hardworking, dutiful 
lord, who certainly does his work well. One nest the lecturer 
kept for some time was constantly attacked by caddis worms, and, 
despite the sentry-like and fighting qualities shown by the male 
stickleback, it got destroyed and the undeveloped eggs rolled out 
and were devoured by the other sticklebacks in the tank, including 
the fickle mother. 
