XI 



PHYLUM ARTHROPOD A 

 ORDER 10. MECOPTERA. 



621 



Insects with four elongated membranous wings (sometimes 

 rudimentary or absent). The mouth-parts are adapted for biting 

 and are borne at the end of a deflexed rostrum. The larvae are 

 caterpillar-like with numerous 

 pro-legs and are carnivorous. 



This order includes the 

 Scorpion-flies (Fig. 525). 



ORDER 11. HYMENOPTERA. 



Insects in which both pairs of 

 wings are present and mem- 

 branous. The mouth-parts are 

 adapted both for biting and 

 licking. The prothorax is united 

 with the other segments of the 

 thorax. There is a complete 

 metamorphosis. 



Included in this order are 

 Bees (Fig. 541) and Wasps, 

 Ants (Fig. 542), Gall-flies, and 

 Ichneumons. 



FIG. 525. A Scorpion Fly (Panorpa com- 

 munist, male. (After Sharp.) 



Systematic Position of the Example. 



The Cockroach is a member of the order Orthoptera, of which 

 there are three divisions, the Cursoria, to which the Cockroaches 

 belong ; the Gressoria, comprising the MantidcB and Pliasmidw, or 

 Stick-and-Leaf insects and their allies ; and the Saltatoria, in- 

 cluding the Grasshoppers, Locusts, and Crickets. The division 

 Cursoria comprises, in addition to the Earwigs, the single family of 

 the Cockroaches (Blattidce), characterised by the deflexed head, the 

 flat oval body, the large prothoracic tergum, the long antennse, 

 the three pairs of legs similar, with large coxse entirely covering 

 the sternal surface of the thorax, the five- jointed tarsi, and the 

 presence of anal cerci. Periplaneta belongs to a section of the 

 family distinguished from the rest by the femora being spiny 

 underneath, and by the valvular character of the last sternum in 

 the female. 



3. GENERAL ORGANISATION. 



The exoskeleton of the Insecta (Fig. 526) consists of a chitinous 

 cuticle (cut.}, which varies in hardness and thickness in different 

 Insects and in different parts of the body of the same Insect, but is 

 very rarely calcified. Frequently it presents hexagonal markings ; 

 sometimes it is perforated by numerous pores ; sometimes it is 



