358 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



SearcliiiiiGj for the eggs of tlie water-bugs might prove useful on a small 

 scale, but would, of course, be useless for the numerous species of Zaitha, 

 which lay their eggs on their own backs. If the collection of the eggs 

 of those species which lay their eggs in masses was attempted, it might 

 be possible to cause the insects to lay their eggs under boards placed 

 in favorable localities in shallow water, and the eggs could be taken 

 from beneatJ^ the boards every few days and destroyed. This mode of 

 destroying nie eggs is ottered as a suggestion, not having had, to my 

 knowledge, any trial. 



Collecting the adult bugs with nets would somewhat lessen their num- 

 bers, but would prove of value only in small ponds, and even these ponds 

 might become restocked with bugs in a single night. Capturing migra- 

 tory insects has little value in lessening their depredations, except where 

 the capturing can be done under very favorable circumstances and over 

 large areas of country. 



Keeping fish jionds clean will certainly be of use in restraining the 

 depredations of water-bugs, as they prefer to live in mud and rubbish 

 rather than in clear water. 



The introduction of some insectivorous fish that will not eat the young 

 fishes would be the most feasible way of ridding a pond of these insect 

 pests, but my knowledge of the habits of fishes is not suflicient for me 

 to state whether any such fish is available for use- in our fresh- water 

 [)onds. A careful study of what is known about the food of our fishes 

 might reveal some species that would keej) water-bugs exterminated 

 from any ponil into which it was introduced. Ducks are known by in- 

 sect-collectors to nearly exterminate the insects from some of the ponds 

 which were the best for the collection of water-beetles before the ducks 

 liiid access to them. Uhler mentions that, in the Harris collection 

 of insects, there is a si)ecimen of a water-bug {Zaitha Jiuminca) bearing 

 the label, " Found in great numbers in the stomach of a duck." But 

 ducks might eat some of the young fishes, thus i)roving their uselessness 

 for the [)ur|»ose intended. Among the enemies of the Helostoinidiv may 

 be mentioned little red mites, which are often seen attached to the joints 

 of the bugs; but these parasites probably cause their hosts but little 

 trouble, and could not be used in any way as a means of their destruc- 

 tion. 



The mode of destroying the water-bugs that seems to me to be the most 

 feasible is by theemi)loymentof the electric light, and even this method, 

 wliicli wouhl onlyi)ayo!i a large scale, might fail to desti'oy a sufiicient 

 number of the bugs to be of practical value. Since the introduction of 

 the electric light as a means of lighting streets, several notices have 

 been published to the effect that, among other insects which are at- 

 tracted to the light and sometimes swarm about in numbers, are the 

 acpiatic hemiptera. Striking against the glass which surrounds the light 

 they fall to the ground. Collectors of insects have taken advantage of 



