CHIEF ENTOMOLOGICAL CLASSIFICATIONS ANU SYSTEMS. 609 



he Linnaean merely in establishing the Orthoptera as an order, and 

 the separation of the Aptera into seven equivalent orders. The following 

 are the seven new orders : 



1. Suctoria (the genus Pulex). 



2. Thysanura (the genera Lepisma and Podura}, 



3. Parasita (the lice, with Ricinus, De Geer). 



4. Accphala (Unogata, F., spiders, scorpions, and Acari). 



5. Entomostraca (the genera Cypris, Daphina, &c.). 



6. Crustacea (Kleistagnatha and Exochnata, F.). 



7. Myriapoda (Mitosata, F., the genera Scolopendra, lulus, 



Oniscus, and allies). 



The author professes to have sought their natural arrangement, and 

 to have founded his divisions less upon a single character than the 

 general expression of the whole ; but the mode in which he has formed 

 his system scarcely supports his proposition, for many unnatural sepa- 

 rations still remain. He, however, claims the positive merit of having 

 introduced the natural families. 



The next arrangement published by Latreille we find in his 

 ' Genera Crustaceorum et Insectorum/ Paris, 1806, 4 vols. 8vo. He 

 here divides, with Cuvier, Linnaeus's Insccta into two equivalent 

 groups, Crustacea and Insecta, the former of which he characterises 

 by the possession of a heart and bronchial respiration, and the latter by 

 respiring through tracheae. The class of insects which alone here 

 concerns us is divided in the following manner : 



I. Insects without wings. Aptera. 



A. With segments bearing seven or more pairs of legs. 



a. Head separated from the thorax. 



a. a. Four antennae. Last segments 1. Legion. Tetracera. 



of the body without legs. 



b. b. Two antennae. All the seg- 2. Myriapoda. 



ments except the last with 

 legs. 



b. Head connected with the thorax. 3. Accra. 



No antennae. 



B. With three segments bearing legs. 4. Aplcrodicera, 



II. Insects with wings. 5= - Pterodicera, 

 A. With elytra and wings. Elytroptera. 



a. With mandibles. Odontata. 



R R 



