196 IOWA ACADEMY OF SCIENCE Vol. XXV, HilS 



Jii fact it is an adaptation, the racial benefit of which clearly 

 depends upon another adaptation, the development of the larval 

 stfige. But why should we have in spiders a eiuiescent stage fol- 

 lo\ving the egg' stage? This point the writer is not ready to 

 answer, but it is interesting to note that the quiescent instar is 

 liore protected, a.s in insects, from most natural enemies. Many 

 insect larvte spin a protecting cocoon before they pass into the 

 quiescent stage. In the house spider the mother has already 

 spun the cocoon to protect her young from enemies during tlieir 

 quiescent period. 



The first, or quiescent nymph (figure 40) ditt'ers from all of 

 the following nymphal instars in being al)solutely unarmed. 



Fig. 40. — First or quiescent, iiyauili l» ihe left ; to the rig-ht the second, 

 or first active nymphal instar. 



Tliere are no spines or hairs of any kind on the body or legs, and 

 the tarsi are without claws. The quiescent nymph is stouter than 

 the other spiderliugs. The legs, instead of being longer than 

 the body, are somewhat shorter than the body. They are not 

 used during this stage. 



The molting process of the quiescent nymph was observed. It 

 was the same as in the other stages. First the skin of the ceplialo- 

 thorax splits around the sides of the lx)dy just above the coxa* of 

 the legs. Then the legs and palpi are slowly extracted from their 

 old ■coverings, and finally the skin splitting along the sides of the 

 ])edicel onto the abdomen releases the lattei". which is drawn out. 

 Presumably there is a molting fluid poured out between the old 

 and new skins which aids in the molting |)roeess. 



