ROLL CALL ^,j 



PHYLUM XII - ARTHROPODA - Lobsters, crabs, spider., millir>odes 

 insects. ' * ' 



Characteristics: External evidence of segmentation, body at least beine 

 divisible into a well-defined head, thorax, and abdomen; jointed append- 

 ages ; chitinous exo-skeleton ; nervous system of ladder f vpo witl, tondcnry 

 toward concentration in head region; main longitudinal blood vessel 

 with heart dorsal to alimentary canal; coelom reduced; body cavity 

 filled with blood (hemocele) ; 640,000 species. 



Class I — Crustacea — Crayfish, crabs, water fleas, barnacles, sowbugs (Cam- 

 barus, Callinectes, Gammarus, Asellus, Trior thrus). 

 Characteristics: Mostly aquatic; usually bearing gills; with two pairs 

 of antennae (feelers) ; chitinous exo-skeleton ; body divided into head, 

 thorax, and abdomen ; head and thorax sometimes fused {cephalolhorax) ; 

 further subdivision depending largely upon characteristics of carapace. 



Class II — Onychophora — Annelidlike arthropods (Peripatus). 



Characteristics: Tropical, primitive, wormlike tyi)os j)resumably inter- 

 mediate between the segmented worms and the arthropods; excretory 

 system of annelid type (nephridial) ; respiratory organ resembles tracheae 

 of insect group ; external appendages ringed, suggesting segmentation of 

 arthropods. 



Class III — Myriapoda — Centipedes and millipedes {Scolopendra, Spirobolus). 

 Characteristics : Body relatively long and definitely nietamcric ; one 

 pair of antennae ; appendages segmented ; legs similar ; respiratory sys- 

 tem of tracheal type ; in millipedes there are two pairs of legs per somit«, 

 in centipedes one. 



Class IV — Insecta — Insects, as butterflies, grasshoppers, beetles, bees. 



Characteristics: L^sually possess wings; one pair of antennae; tracheal 

 respiratory system ; segmented legs. 

 Order 1 — Thysanura — Bristletails, Silverfish (Lepistna, Campodea, Thermobia). 

 Characteristics : Wingless arthropods ; primitive ; probably derived from 

 wingless ancestors ; 11 abdominal segments; chewing mouth parts; usu- 

 ally two or three long, threadlike, segmented caudal appendages; less 

 than 20 species in the United States ; no metamorphosis. 

 Order 2 — Collembola — Springtails (Archorules). 



Characteristics : Primitive wingless insects with chewing or sucking mouth 

 parts; four segmented antennae; usually no tracheae; six abdominal 

 segments; a springing organ (furcida) present on ventral side of fourth 

 abdominal segment in most species ; no metamorphosis. 

 Order 3 — Orthoptera — Grasshoppers, cockroaches, walking sticks {Melanoplus, 

 Periplaneta, Diapheromera). 

 Characteristics: Members of this order are characterized by two pairs 

 of wings (sometimes greatly reduced) ; the fore wings usually thickened. 

 sometimes leathery ; hind wings folded fanlike beneath fore wings ; biting 

 mouth parts ; gradual or simple metamorphosis. 



