MOSQUITO BIOLOGY 89 



the insects are not altogether beyond our reach as the following experi- 

 ments, carried on under the direction of Professor Smith, will show. 



Experiments with Phiiiotas Oil. October 7: A small amount of the 

 oil was put into a jar containing about one gallon of water and sixty 

 larvae. It had no immediate effect upon them, but in two or three hours 

 afterwards such as were swimming free in the water were seen to be slug- 

 gish in their movements. The next day, about twenty hours after the 

 application, the water and grass sod were examined, and while most 

 were dead three larvae were washed from the sod, which were active and 

 swam freely when changed to fresh water. 



An approximately similar amount of the oil was put into a jar con- 

 taining two gallons of water and 100 larvae. The oil in this case was 

 forced down into the water by means of a pipette and bulb, Avhereas in 

 the first jar it was put in gently. The material sank to the bottom very 

 slowly and it was fully two hours before it actually enveloped the sod. 

 The next day, twenty hours afterward, only two larvae were alive from 

 the sod ; the remainder were dead. 



October 10: I went to Trenton and selected a spot in the swamp 

 where larvae were present ; six were taken by the first dip of a net and 

 four in the second. Here I staked out an area twelve feet square and 

 from a sprinkling can poured one gallon of Phinotas oil evenly over the 

 surface. The area, as in the whole swamp, is thickly overgrown with 

 vegetation and at this time of the year was worse than in summer be- 

 cause of the dry grass falling down and forming a layer over the sur- 

 face which must be penetrated before the grass roots, where the larvae 

 cling, are reached. 



October 15: I thoroughly examined the area treated with Phinotas 

 oil on the tenth. Two hours were spent in fishing around the tussock 

 tufts, as well as elsewhere, and in that space of time I secured only four 

 larvae, two dead ones and two that were very much alive. Thus it ap- 

 pears that dead larvae are not so easily secured as are live ones since 

 larvae were really abundant before the application. 



About ten feet distant from the area treated with Phinotas oil larvae 

 were as numerous as previously, even though a thin coating of oil was 

 present over the surface where it had spread from the treated part. 



DESCRIPTION OF THE LARVA 



Length 6-7.5 mm. (.24-30 inch) from head to end of ninth abdom- 

 inal segment. Robust, resembling in life larva of PsoropJwra columbine. 

 White, tinged with clear transparent green which is often predominat- 

 ing hue. Head pale brown, much broader than long, rounded in front 



