ENTOMOLOGY 



segmented. Body elongate, with fifteen distinct terga, and eleven or 



weTve pairs of legs. Cerci well developed. Genital opening m the 



mrd body segment. One pair of spiracles, opening on the head, under 



e antennae Small arthropods not more than five or six millimeters 



in length. Example, Scokpendrella (Fig. 6). 



Myrientomata.-Terrestrial. Three regions: head, 

 abdornTn. Head small, conical, prognathous. One pair of eye- 

 spots. Antenna absent. Mouth parts suctorial. Mandibles 

 maxillae attenuate, styliform, protrusible and retractile. Labium 

 attenuate Body strongly elongate, fusiform, narrowing posteriorly, 

 Segmented* adults. Thorax distinct from abdomen- prothorax 

 shorter Sn meso- or metathorax. Three pairs of thoracic legs, and a 

 pair of vestigial legs on each of the first three abdominal segment 

 Last four abdominal segments more or less retractile Cera a 

 Genital openmg posterior. Male genitalia elongate, retractile dually 

 Sotd, with a pair of slender, forceps-like appendages. Female appen- 

 dage short, with short forceps. Minute delicate arthropods seMom 

 more than one millimeter in length. Example, Acerenlonon ( 



A single order, Protura, discovered and named by Silvestn, and 

 consisting of two families: Acerentomidae, without a trachea! s 

 and Eosentomidse, with simple tracheae and two pau-s o thoracic 

 spiracles. Protura, easily overlooked on account of their small 

 doubtless widely distributed. At present twelve species are knownfr 

 Europe and twelve from the United States, all but one of our species 

 having been described by Dr. H. E. Ewmg. 



Insecta (Hexapoda). -Primarily terrestrial. Three distinct regions 

 -head thorax and abdomen. Head with a pair of compound eyes 11 

 most adults, one pair of antennae and typically three pairs of mouth 

 .arts-mandibles, maxillae and labium-besides Which a hypopharynx, 

 or tongue, is present. In Apterygota a fourth pair of mouth parts 

 associated with the hypopharynx. Thorax with a pair of legs on each 

 of its three segments and usually a pair of wings on each of the post 

 two segments; though there may be only one pair of wings (as m Dipt. 

 male Coccidse and male Strepsiptera) ; the prothorax never bears wings. 

 Abdomen typically with eleven segments and without legs, excepting m 

 some larvae (as those of Lepidoptera, Tenthredinidae and Panorpidae) 

 Stigmata paired and segmentally arranged. A metamorphosis (direct 

 or indirect) occurs except in Thysanura and Collembola. 



Relationships. The interrelationships of the classes of Art 

 form an obscure and highly debatable subject. 



