16 
Charles K. Biernbaum 
seasons. However, because females were not identified (taxonomically 
important morphological characters were variable and overlapping in 
these species), caution is urged when interpreting such reproductive 
data. 
Caecidotea laticaudata was most extensively distributed in the 
summer (Table 2), when it was numerically most abundant. Although 
found in various habitats, frequently co-occurring with C. forbesi, C. 
laticaudata was largely restricted to the lake margin of the refuge units, 
plus some immediately adjacent aquatic habitats such as impoundments 
or swamps. Like C. forbesi , it was common in swamps; however, it did 
not occur in such habitats in the interior of the units, as did C. forbesi. 
Unlike C. forbesi , C. laticaudata was at times abundant in certain 
impoundments next to Lake Marion. During the winter this species 
occurred only in a few sunlit impoundments. Caecidotea laticaudata 
occurred in shaded areas only in summer. At refuge sites where only C. 
laticaudata was collected (based on identification of males), brooding 
females were found in January and June. As mentioned above, one 
must be cautious when using data based on unidentified females, 
particularly because reproduction in January of a species like C. 
laticaudata , which is rare in winter and abundant in summer, would be 
unexpected. 
Differences exist between refuge units with respect to occurrences 
of Caecidotea species. These differences most likely result from inter- 
unit variations in lake proximity and types of aquatic habitats present. 
Prime examples are comparisons of the Bluff and Cuddo units. Bluff 
unit is very narrow, with most of its area close to the lake; considerably 
less than half of Cuddo unit is as close to the lake as is all of Bluff unit 
(see Fig. 1). Bluff unit also has much more of its aquatic habitats 
consisting of impoundments, rather than swamps or ditches, than does 
Cuddo unit. Most likely due to these differences, C. laticaudata is the 
dominant isopod in the Bluff unit and C. forbesi in the Cuddo unit. 
As mentioned above, there is considerable seasonal variation in the 
degree of flooding of aquatic habitats. In the dry summer and fall most 
of the shallow habitats for C. forbesi dry out, greatly reducing the space 
available for it and, as a result, its abundance. Parsons and Wharton 
(1978) have reported a similar reduction in numbers of an unidentified 
species of Asellus (= Caecidotea) when water levels dropped in summer 
on a Georgia flood plain. However, because C. laticaudata is more 
common in impoundments, seasonal dryness has far less effect on it. 
Lirceus lineatus is widespread in the refuge from fall to early spring 
(Table 2). During the winter it reaches its greatest abundance, 
making up a substantial portion of the aquatic isopod fauna (Table 3), 
but it virtually disappears in the summer. It was found in a wide variety 
