EXPERIMENT STATION BULLETINS. 



259 



attempted this year, but it is hoped that considerable water can be dis- 

 posed of before another year. Oil was used liberally at the rate of one 

 ounce to fifteen square feet of water. The grade known as light fuel oil 

 was used. This cost about $8.50 F. O. B. at Detroit, or a little less than 

 |4.50 per barrel at the College. Its effect lasts at least three weeks, that 

 is, it lasts one week before it ceases to kill larvae and two weeks are 

 usually required for the insect to mature from the egg. The oil kills much 

 of the vegetation. 



Fi^. i. Larvae and eggs of non-mahirial mosquito, from Howard. U. S. Dept. of Agr.. Bui. 25. n. s. 



There are several other aquatic pupae which may be mistaken for 

 the wigglers, notably those of Corethra, Many times the pupae of this 

 fly were brought to us, under the impression that they were mosquito 

 wigglers. Crustacea and insects with closed tracheal systems usually 

 are not killed by the oil, thus larva of Corethra and May-flies lived with 

 little if any inconvenience, and the fairy shrimp was distressed but was 

 not killed. 



PISH. 



Dr. Howard highly recommends the introduction of small sun-fish 

 and sticklebacks in places where they may be expected to live. Sun- 

 fish were introduced into the pond near the woman's building, and sun- 

 fish and sticklebacks into a deep pond in the elk-park. Sun-fish were 

 already present in several ponds in the botanic garden. In none of 

 these places were wigglers found except in the pond near the ^woman's 

 building and in this only after the confervae off'ered good hiding places 

 for them. 



