CHAPTER VII 

 ORDER PROTURA 



The Tclson-Tails 



The members of this order are small arthropods in which the body is 

 elongate, as in the Thysanura, fusiform, pointed behind, and depressed; 

 it may be greatly extended and retracted. The antennce, cerci and 

 compound eyes are absent. The oral apparatus is suctorial, and consists 

 of three pairs of gnathites. There are three pairs of thoracic legs, and 

 three pairs of vestigial abdominal legs. The abdomen is composed of 

 eleven segments and a telson. The opening of ihe reproductive organs is 

 unpaired, and near ihe hind end of the body. The head bears a pair of 

 organs, termed pseitdocidi, the nature of which has not been definitely 

 determined. The metamorphosis is slight, consisting of an increase in 

 the number of abdominal segments. 



The known members of this order are very small arthropods, 

 the body measuring fron one fiftieth to three-fiftieths of an inch in 

 length. The form, of the body is shown by Figure 36, p. 25. 



These exceedingly interesting creatures are found in damp situa- 

 tions, as in the humus of gardens. They are widely distributed: 

 they are now known to occur in India, England, Italy, and other 

 European countries. A number of species have been described from 

 the southwestern United States. 



The mouthparts are withdrawn into the head and the mandibles 

 are stylet-like and fitted for piercing. In the newly hatched insect 

 the abdomen is 9-segmented, but during later growth three more 

 segments are added between the last two segments. This mode of 

 change in form is known as anamorphosis. 



The systematic position of the Protura is still unsettled. The 

 differentiated thorax with three pairs of legs and the form of the 

 mouthparts are characteristic of insects. The lack of antennae 

 and the intercalary addition of body segments during growth (ana- 

 morphosis) are very unlike insects. The name Protura refers to the 

 last telson-like segment of the abdomen. 



The order contains two families as follows : 



Family i. Acerentomid^, in which the tracheae and spiracles 

 are absent and the second and third abdominal appendages are i- 

 jointed. This family includes the two genera Acerentomon and 

 Acerentidus. 



Family 2. Eosentomidae, in which tracheae are present with two 

 pairs of thoracic spiracles and the second and third abdominal 

 appendages are 2-jointed. This family includes the genus Eosen- 

 tomon and probably Protapteron. 



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