10 BULLETIN 416, U. S. DEPARTMENT OF AGEICULTUEE. 



FIRST NYMPHAL STAGE (THE PROTON YMPH). 



As has been stated previously, it is only the female which passes 

 through a second nymphal stage. 



Description. — The primary nymph (PL II, fig. 3) differs from the 

 larva in having 4 pairs instead of 3 pairs of legs, in the somewhat 

 increased size, and in the more oval outline of the body. Furtherr 

 more, the bristles are slightly longer, and the segments of the legs 

 become elongated in proportion to their width. The color of the 

 protonymph is usually darker than that of the preceding stage and 

 the lateral pigment blotches become more evident in this stage. 

 One of the most noticeable modifications in the primary nymph is 

 the considerable elongation of the abdomen, the suture separating 

 the latter from the . cephalothorax lying in a position sHghtly more 

 than one-third the body length from the anterior margin of the 

 cephalothorax, whereas in the larva the suture nearly bisects the 

 body. A series of measurements of the protonymph averaged, 

 length, 0.213 mm.; width, 0.145 mm. 



The habits of the primary nymph are similar to those of the larva. 

 It moves about more freely than the larva. Investigators of red 

 spiders have claimed that the ability to spin webbing appears for the 

 first time in the protonymph, but no effort has been made to estabhsh 

 this point. 



^' PremoUing" period. — Perkins (1897) makes no mention of a qui- 

 escent period preceding the molting of the primary nymph . Ewing's 

 life-history table shows an average duration of If days for the resting 

 period before the molting of this stage. At Batesburg the "pre- 

 molting" period of the protonymph occupies a very few hours. Dur- 

 ing these quiescent periods the body assumes a pearly or silvery 

 appearance. Von Hanstein (1902) called this quiescent period of 

 the primary nymph the "Deutochrysallis.'' 



Duration of the protonymphal period. — With the records of 6 indi- 

 viduals upon which to base his conclusions, Ewing found that in 

 Oregon the protonymphal stage required from 2 to 4 days, with an 

 average of 3.16 days. At Batesburg 37 colonies completed the pri- 

 mary nymphal stage. In March, in one case, this stage required 6 

 days for completion, but in the summer the period is occasionally 

 concluded in 1.5 days. The average duration of the female proto- 

 nymphal stage for aU records at Batesburg is 2.18 days. 



Molting process. — Of all the red-spider stages, those which are dis- 

 tinguished with the greatest difficulty are the primary and secondary 

 nymphs of the female. It is natural to presume, therefore, that no 

 radical changes occur in connection with the molting process, and 

 this is borne out by observations. The time required was slightly 

 over 3 minutes in the case of the one operation observed. (See 

 fig. 3 for the cast skin of the protonymph.) 



