IQ MISC. PUBLICATION 336, U. S. DEPT. OF AGRICULTURE 



stool at the selected place, with the trouser legs rolled to the knee. 

 After a minute or so has been allowed for the mosquitoes to accumu- 

 late, they are collected as they alight, for a period of 10 or 15 minutes 

 (78). If the collecting is done after dark, a flashlight is necessary. 

 Two 15-minute collecting periods or three 10-minute periods may be 

 totaled and multiplied by 2 for the hourly rate. Collections made 

 during the first flight period (just at dark) should not be averaged 

 with later collections, as the numbers are usually much larger at 

 that time. 



When the mosquitoes are numerous, the numbers caught can be 

 increased considerably by placing a short paper funnel, or guard, in 

 the mouth of the collecting tube (fig. 5), since this permits the 

 collector to move to the next specimen without waiting for the first 

 one to succumb to the chloroform fumes. The guards are useful 

 otherwise in conserving the strength of the cholorform and in pre- 

 venting the loss of specimens when the mouth of the tube is turned 

 downward. 



When collecting after dark, the writers have taken an average of 

 10 mosquitoes per minute, or 600 per hour, with a tube of this sort. 

 If the mosquitoes are much more numerous than this, the discom- 

 fort of collecting is so great that it is considered sufficient to record 

 abundance as 600+, or other observed rate, per hour. When the 

 collecting is to be done at different places by two or more persons, 

 preliminary collections should be made at one place to determine the 

 relative attractiveness and dexterity of the different collectors, as 

 much variation has been found in these respects. 



HAND COLLECTIONS OR COUNTS OF RESTING MOSQUITOES 



Some species can be obtained by daytime collecting in dark corners 

 and other places where the adults (including the males) spend the 

 daylight hours. This is an excellent method of obtaining compara- 

 tive data on adult densities of Anopheles, especially those species 

 found in the United States, since they fly into a shelter at daybreak 

 and remain quietly there throughout the day. For these species also 

 this method is much safer than the biting method, which is attended 

 with danger of malaria transmission. 



Favorable daytime resting places for Anopheles are found under- 

 neath buildings that are raised 2 or 3 feet from the ground and inside 

 tightly boarded outbuildings or similar locations. In making the 

 surveys a series of stations well distributed over the area under ob- 

 servation are selected, and weekly, biweekly, or monthly collections 

 are made (65, 72) . At each location the most favorable resting place 

 should be selected after examination of all the buildings on the 

 premises. When the surveys are purely for comparative purposes, 

 the collecting station does not always need to be an entire building, 

 if it is found that one part is more favorable than another or that 

 parts of the building are not conveniently accessible. Where the 

 resting surface is fairly smooth and unobstructed, a well-trained and 

 reliable collector, with the aid of a flashlight, can obtain satisfactory 

 counts of the resting mosquitoes in much less time than would be 

 required for collecting the specimens in killing bottles. The sex can 

 be determined and in most cases the species identified on sight. Col- 

 lections over a definite period (10 or 15 minutes) have been used as 



