MICROSCOPIC OBJECTS. 63 



Fig. 125. House-Cricket (Acheta domestica), natural size. 

 Order Orthoptera. 



The order Orthoptera contains some of the most interesting 

 insects in regard to their structural characteristics. Among 

 the most remarkable may be mentioned the Mantis, Cock- 

 roaches, Earwigs, Locusts, Crickets, &c. The description of 

 the general structure of this order is as follows : " Wings 

 four, the upper coriaceous, veiny ; the inferior membranous, 

 longitudinally plaited like a fan j mouth serving for mandu- 

 cation, with strong mandibles; maxillse furnished with a 

 cylindrical helmet : metamorphosis incomplete." 



The House-Cricket is one of the best insects for an amateur 

 to dissect, as the organs are tolerably large, and at the same 

 time interesting. Small specimens may be mounted in bal- 

 sam after the usual treatment for insects. 



Fig. 126. Eye of Locust (Acrydium migratorium), x 80. 



The eyes of insects vary much in size, and also in the 

 number of facets composing a single eye. Some of the 

 largest are to be found in the Libellulae (Dragonflies) ; but, 

 from the size of the facets, the eye of the Locust may be con- 

 sidered one of the first. Insects see differently from us, 

 as each of the facets answers to the single eye of a higher 

 animal ; therefore the objects are reflected to them in much 

 larger numbers, and no doubt this acute impression that their 

 brain receives causes that extreme quickness of sight for 

 which most insects are remarkable (see the various insect- 

 eyes). Many of the eyes are best mounted dry, after being 

 well washed, &c. ; others are best when mounted in fluid ; 

 and scarcely any show well in balsam, as it makes them too 

 transparent. 



