416 ANISrUAL REPORT SMITHSONIAN" INSTITUTION, 19 31 



bladders capture mosquito larvae and how many? Franca (1922) 

 observed them capture numerous larvae oiTheohaldia longiareolata 

 and Anopheles hifurcatus; Brumpt (1925) records the capture of the 

 larvae of Anopheles maculipennis and Culex apicdHs. During the 

 summer of 1929, I carried on a few experiments with this plant to 

 determine the rate of destruction and the size of larvae they could 

 capture. Plate 2, Figure 2, shows a small branch containing 10 

 active bladders. In five of these may be seen mosquito larvae in 

 various stages of digestion. I have had them capture the smallest 

 larvae and readily destroy the largest larvae I could obtain. Two 

 preliminar}' experiments were conducted to determine the effective- 

 ness of this plant in small aquaria. Two small branches were placed 

 in a battery jar with 50 young larvae of Culex territdns. On the 

 following day only two free larvae could be found; the bladders 

 contained the others. During the next four days 375 larvae were 

 added and practically all were captured, though toward the end of 

 the experiment nearly all the bladders had dropped from the 

 branches. How long a single bladder may live and how often it 

 can capture such large prey as mosquito larvae, are not known. In 

 another similar experiment, 225 larvae were added and practically 

 all these were captured before the bladders began falling from the 

 plant. 



In order to test the size of animals captured, large larvae of 

 Brachydeutera argentata Walk. (Ephydridae, Diptera) were added 

 to an aquarium with Utricularia. The results are shown in Plate 1, 

 Figure 2. In cultures of Utricularia large numbers of these larvae 

 were readily captured. Though only a small portion of the larva 

 is first taken into the bladder, our observations show that eventually 

 the entire larvae is absorbed. How tliis is done is not easily 

 explained. 



Though the captured food of the Utricularia would appear to bo 

 mainly small organisms belonging to the Crustacea, Protozoa, etc., 

 yet it would seem that this group of plants deserves more considera- 

 tion as a possible agent in mosquito control. The bladderworts are 

 very graceful plants, grow luxuriantly where they occur and ought 

 to make an added attraction in fishponds, small lakes, private pools, 

 etc. Unfortunately we know very little about their biology or 

 methods of their culture. 



SURFACE-COVERING PLANTS 



Another group of plants that has attracted considerable attention 

 among students of the mosquitoes comprises the surface-covering 

 aquatic plants. These plants are often packed so closely together 



