sapidus and R. harrisii were brought in from the waters of the Newport Estuary 
in the vicinity of Beaufort, North Carolina, and maintained in salinities and 
temperatures most closely approximating those of the experimental conditions 
until hatching of the larvae occurred. With the experiments on 
Rhithropanopeus harrisii, the larvae were set up in separate experimental series 
consisting of 50 larvae per species, and maintained in temperature controlled 
cabinets with a photoperiod of 12 hours light and 12 hours dark, until the 
fourth juvenile crab stage was reached. 
In experiments with Callinectes sapidus, which involved only the megalopa 
stage, larvae were maintained through the seven zoeal stages of 30 ppt, 25°C 
until the final zoeal molt. At that time, 20 megalopa were transferred to each 
of the experimental salinity and temperature conditions, and maintained in a 
photoperiod consisting of 12 hours light and 12 hours dark until the fourth 
juvenile crab stage was reached. Within each of the experimental series a 
control series was maintained, and at least one acetone-control series was 
maintained, since both methoprene and MONO-585, only slightly soluble in 
water, were prepared from the pure compound as an acetone stock solution of 
1 ppt. 
The two compounds used in this experiment were methoprene (Altosid^: 
ZR-515; isopropyl 1 l-methoxy-3, 7, 1 l-trimethyldodeca-2, 4-dienoate) 
manufactured by Zoecon Corporation, Palo Alto, California, and MONO-585 
(2, 6-di-t-butyl-4- (aadimethylbenzyl) phenol) manufactured by Monsanto 
Chemical Company, St. Louis, Missouri. 
In the experiments on Rhithropanopeus harrisii larvae involving MONO-585, 
dilutions of 10, 1 and 0.1 ppm were used in combination with 25°C, known 
from previous work to be the optimum temperature for development (7), and 
salinities of 5, 20 and 35 ppt. 
In experiments with Callinectes sapidus megalopa, a variety of salinities, 
constant temperatures, and cyclic temperatures were combined with the 
dilutions of MONO-585 (10, 1,0.1 ppm) or methoprene (0.1 and 0.01 ppm). 
These included, depending on the particular series, salinities ranging from 5 to 
35 ppt and temperatures, constant or cyclic, ranging from 20°C to 35°C. The 
specific conditions for individual experimental series will be considered in 
connection with the results. 
Larvae in all series were checked each day for survival and stage of 
development, the numbers being recorded for each experimental series. 
Individual megalopa were segregated in plastic compartmented boxes to avoid 
cannabalism, and also to facilitate recording the time of metamorphosis to the 
first and subsequent crab stage for each individual. 
322 
