Head Width 
360 
Psyche 
[Vol. 92 
3.0 
2.0 
E 
E 
1.0 
0 
ONDJ FMAMJ JAS 
Month 
Figure 2. Growth of Baetisca Carolina nymphs based on mean monthly head 
widths. Solid line represents female growth; broken line represents male growth. 
no growth occurred in the winter months, but as the water tempera- 
ture began to rise, growth began to occur. Nymphs showed the 
greatest head width in April, while they exhibited a decline in mean 
head width in May and June. This decline is due to the emergence of 
the larger nymphs. The large growth rate in July is probably due to 
nymphs growing in preparation for a second emergence in August. 
These data, along with data from nymphal exuviae and length- 
