26 INTRODUCTION 



SUBKINGDOM IX. ANNULA'TA (with rings): Worms with seg- 

 ments apparent externally. Earth worm 

 and leech (Figs. 178, 179). 

 SUBKINGDOM X. MOLLUS'CA (soft): Soft-bodied forms usually 



with a shell. Oysters, snails, slug, squid. 

 SUBKINGDOM XL ARTHRO'PODA (jointed feet) : Segmented forms 



with jointed legs. Crabs, beetles, wasps. 



Class 1. Crusta'cea (crust) : Arthropoda with head and thorax 

 fused and usually a hard outer skeleton. Crayfish (Fig. 155), 

 lobster, pill bug (Fig. 164). 



Class 2. Myria'poda (thousand-footed) : Forms with air tubes 

 throughout the body and numerous legs. Centipeds (Fig. 

 152), millepeds (Fig. 153). 

 Class 3. Arach'nida (spider) : Forms with usually four pairs of 



legs and no antennae. Spiders, scorpions (Figs. 144-151). 

 Class 4. Insec'ta (cut-in) : Forms with body showing three dis- 

 tinct parts called head, thorax, and abdomen ; and breathing 

 by means of tubes ramifying among the tissues and opening 

 on the lateral aspect of the body (Figs. 9, 10). 

 Order a. Ephemer'ida (lasting one day) : Forms with two unequal 

 pairs of wings, no mouth parts, and two or three filaments 

 projecting from the end of the abdomen. May fly (Fig. 139). 

 Order b. Odona'ta (tooth) : Forms with four nearly equal mem- 

 branous wings. Dragon flies, damsel flies (Figs. 140, 141). 

 Order c. Orthop'tera (straight-winged) : Forms usually with 

 four wings, the hinder ones being thin and overlapped by the 

 thick fore wings when at rest. Grasshoppers, crickets, cock- 

 roaches (Figs. 11, 13). 



Order d. Hemip'tera (half-winged) : Forms which take food by 

 sucking only. Bedbug, cicada, plant lice, scale insects 

 (Figs. 98, 107). 



Order e. Neurop'tera (nerve-winged) : Forms with two pairs 

 of membranous net-veined wings. Dobson or hellgramite 

 (Fig. 138). 



Order f. Lepidop'tera (scale-winged) : Forms with two pairs 

 of wings covered with overlapping scales. Butterflies, 

 moths, millers. 



