I9 2 ELEMENTARY ZOOLOGY 



number of orders by breaking up some of the old ones 

 into two or more new ones. The classification adopted 

 in the text-book * of zoology which we have made our 

 reference in classification is an 8-order system. The 

 latest English t text-book, in entomology adopts a 

 9-order system, while the principal American J text-book 

 on this subject divides the insects into nineteen orders. 



The classification depends chiefly on the character of 

 the post-embryonic development, that is, on whether the 

 metamorphosis is complete or incomplete, and on the 

 structural character of the mouth-parts and wings. In 

 the following paragraphs a few of the larger insect orders, 

 with some special representatives of each, will be briefly 

 considered. 



The best American text-book of the classification and 

 habits of insects is Comstocks' "Manual of Insects." 

 For an account of the structure of the wings and mouth- 

 parts of various insects see Comstock and Kellogg 's 

 " Elements of Insect Anatomy." 



Orthoptera : the locusts, cockroaches, crickets, katy- 

 dids, etc. TECHNICAL NOTE. Obtain specimens of crickets or 

 katydids, and cockroaches, and compare the external body struc- 

 ture with that of the grasshopper; examine especially the wings, 

 mouth-parts, legs, and egg-laying organs. Note that the hindmost 

 legs of the cockroach are not fitted for leaping but for running. Note 

 the sound-making (stridulating) organs on the bases of the fore wings 

 of the male katydids and crickets. Note the auditory organs (tym- 

 pana) in the fore tibiae of the katydids and crickets. Crickets can 

 be easily kept alive in breeding-cages in the laboratory and their 

 feeding habits and much of their life-history observed. The growth 

 of the young and the development of the wings can be noted, and 

 will be found to be essentially similar to the conditions already 

 found in the case of the locust. 



The locust studied as one of the examples of the class 

 Insecta belongs to the order Orthoptera, which also in- 



* A Text-book of Zoology, Parker & Haswell, 1897. 



f The Cambridge Natural History, vol. V, 1895. vol. VI, 1899. 



| A Manual for the Study of Insects, J. H. and A. B. Comstock, 1897. 



