98 INVERTEBRATE ANIMALS. 



seem to apply more appropriately to the gre- 

 garious and migratory species included in the 

 following group. 



Observe the closeness of the resemblance between 

 several species of Locusts and the leaves of 

 trees in various stages of decay. This 

 mimetic perfection may be regarded as the 

 result of progressive improvements on the 

 part of the assailants, as well as on the side 

 of the species protected by disguise ; indi- 

 viduals on the one side becoming more and 

 more mimetic, and on the other (that of their 

 enemies) more and more able to penetrate 

 through the assumed disguises. — {The Natu- 

 ralist in Nicaragua, by Thomas Belt, 1874.) 



Group 228.— Family ACEIDIID^. axpis, the grasshopper. 

 Migratory Locusts, Grasshoppers, &c. The ravages for 

 which these insects have long been notorious have not 

 been confined to a single country ; nor have they always 

 been committed by the same kind of locust. Africa 

 seems to have sufiered most frequently and severely, but 

 Europe, North and South America, and the East have 

 from time to time been subject to their visitations. 

 Series of British species, presented by B. Cooke. 



The Mark 5[ indicates specimens or other illustrations exhibited in the Cases. 



Group 229.- Families ACHETIDiE and BLATTID^. 

 Crickets, Achetidce. rjx^T^s, an utterer of shrill sounds. 



