THE BED SPIDER ON COTTON. H 



SECOND NYMPHAL STAGE (THE DEUTONYMPH). 



Description. — The deiitonymph, which occurs only m the case of 

 the female, resembles the protonymph except that it is larger and 

 more elongate. In the advanced condition of this stage (PI. II, fig. 4) 

 it also resembles the adult female. Although pigmentation is intensi- 

 fied as the mite approaches maturity, there is usually an absence of the 

 characteristic reddish color. As the deutonymph approaches matu- 

 rity it can be distinguished from the maturing male nymph, as the lat- 

 ter is smaller, more cimeate posteriorly, and exhibits a tinge of amber 

 or ferruginous. K series of measured deutonymphs averaged, 

 length, 0.360 mm.; width, 0.218 mm. 



Duration of the deutonymphal period. — Perkins (1897) found that 

 in Vermont an average of 2 days was required for the completion of 

 the second nymphal stage under summer conditions. Swing's 5 

 completed deutonymphal breedings averaged 2.6 days. The portion 

 of this interval occupied by the quiescent period 

 (the " Teleiochrysallis " of von Hanstein) is not 

 clearly indicated in Ewing's bulletin, but appears 

 to be approximately 1 day. 



In the Batesburg investigations 25 colonies 

 completed the second nymphal stage of the 

 female. One deutonymph, the egg of which was 

 deposited on September 27, required 13 days for 

 its development. Exhibiting the other extreme, 

 a few individuals of this stage matured in ap- 

 proximately 1 .25 days in midsummer. The aver- 

 age duration for the second nymphal stage during 



.1 ,• • 1 r\ J Fig. 3. — Cast skin of the 



the active season is 1 .9 days. ^^, ^pj^^^ ^^^^ ^, ^^^ 



Habits. — The deutonymph is probably the time of second moit, stiii 

 most voracious of the immature mites. It roves l^^^ ( original. r^""^' 

 about considerably on its native leaf, Ewing 

 (1914) records a well developed spinning ability on the part of the 

 deutonymph. The first two stages are not adapted to traveling 

 over the soil surface, owing to their frailty, but the last immature 

 state is more hardy and active, and individuals are often capable 

 of successfully establishing themselves after traversing considerable 

 distances. This fact has been determined by "tanglefoot" tests, and 

 by finding deutonymphs on cotton seedlings which were younger 

 than the mites. 



Molting jyrocess. — Upon two oc(;asions, in the early morning, 

 females issued from the second nymplial skin. The transverse 

 split occurs practically as in the two pi-eceding molts. In one in- 

 stance, following a night minimum of 46° F., the morning was cool, 

 and this condition doubtless worked to retard the duration of tlie 

 proeess, which o(;cupied nearly 4 minut(^s. The other observed 



