108 
Mary Beth Roush and Donald C. Tarter 
remains alive is black willow, Salix nigra Marsh. Button-bush saplings, 
Cephalanthus occidentalis L., have the greatest density of any woody 
plant seedling in the swamp. 
This study was initiated in December 1977 and completed in December 
1978. Larval collections were made on a monthly basis during the study 
period. However, due to the lack of specimens in certain months, we 
decided to select one month as a representative of each season and report 
all calculations on a seasonal basis. 
Water quality tests were performed at the collection site with a Hach 
chemical kit. Model AL-36B, and pH was measured colorimetrically. 
Dissolved oxygen, carbonate alkalinity, and total hardness were meas- 
ured and recorded in mg/ 1. Water temperature was taken with a Taylor 
maximum-minimum thermometer placed 0.3 m below the water surface. 
Larvae were collected from mud and leaf debris using a long-handled 
dredge with a mesh size of 60 threads/ inch, and preserved in 70 percent 
ethanol. Total length of larvae was measured to the nearest 0.5 mm using 
a centimeter rule. Size classes were determined by length-frequency his- 
tograms arranged in 2 mm length groups. Head width, measured to the 
nearest 0.01 mm with an ocular micrometer, was used to assess growth. 
Differences in larval head width were used to calculate the mean, range, 
standard deviation, and standard error of the mean. Percent growth from 
one season to the next was calculated using the mean head width value. 
Larval instar designations were determined by using head width 
measurements. 
Seventy-four larval foreguts were examined to determine food habits. 
The head was removed with microdissecting scissors and the abdomen 
split dorsally to remove the foregut. Contents of the foregut were 
removed for a complete scan with dissecting binocular microscope, then 
transferred to a compound microscope for identifications. The entire 
slide was quickly scanned for large remains, and a running tally of major 
taxa was kept on a composite sheet. The number of foreguts containing 
one of these taxa was recorded, the mean determined, and the data 
analyzed by percent frequency of occurrence. A grid method was used to 
determine the amount of detritus and diatoms. Using a Whipple eyepiece 
consisting of 100 grid squares, each foregut was examined in three differ- 
ent fields (300 grid squares) and a record made of presence or absence of 
detritus or diatoms in each square. A mean was determined for each 
foregut and the data were analyzed by percent frequency of occurrence 
per 100 squares. 
Larval case length measurements were made to the nearest 0.5 mm 
with a centimeter rule. The number of rings in each case was recorded 
and each ring length measured to the nearest 0.5 mm. Using a dial Vern- 
ier caliper, the diameters of the anterior and posterior openings of each 
