380 



APPLIED BIOLOGY 



In order to make observations on the habits of myriopods, 

 collect them from under logs and stones in early autumn, and 

 keep in closed boxes with pieces of bark, chips, and leaves 

 under which they can conceal themselves. Keep moist, not 

 wet. Feed with flies, earthworms, or bits 

 of fresh meat for centipedes; various 

 vegetable foods for millipedes. 



That myriopods are closely related to 

 insects is shown by many points of struc- 

 ture, both external and internal. But they 

 are evidently lower than insects, for they 

 have no wings and the body does not show 

 differentiation into head and thorax. 



A. B 



FIG. 130. Two myrio- 

 pods. A, milliped 

 with two pairs of 

 legs on each seg- 

 ment (really two 

 combined segments) . 

 B, a centipede. 

 (From Thomson.) 



References : Davenport's " Zoology," Chap- 

 ter V. Jordan and Heath's " Animal Forms," 

 pp. 111-113. 



INSECTS 



322. Prominence of Insects. Aside 

 from the domesticated animals which be- 

 long to the higher vertebrates (birds and 

 mammals), the insects are of more importance in economic 

 relations than are all other groups of animals taken together. 

 But quite apart from practical matters, the insects have long 

 keen favorite objects for study because many are beautiful, 

 many have remarkable adaptations to special conditions of 

 life, and many have wonderful instincts and nervous activities 

 which are surpassed only \>y certain birds and mammals. 



More than half of the known species of animals are insects. 

 From 200,000 to 250,000 species are now known, and many 

 newly-discovered species are named and described each year. 

 Some experts in entomology (that division of zoology which 

 deals with insects) believe that there may be living now a 

 million species of insects. 



It is a fortunate fact for students of insects that they are all 



