Size o[ Mesh, Not Shape, is the lmportant Factor In lnsect Wire Screening

Bv Ralph \7. Bacon. Secretary, War-ernergencv 18 x 14 mesh insect wire screening is equal in protective efficiency to 16 x 16 mesh, but is less effective against smaller insects than 18 x 18 mesh, according to recent scientific tests made by, trvo leading r.rniversities for the insect rvire screening industry.

I'he tests, begun this past summer at the University of lilorida and the University of Delarvare, shorv conclusively that size of mesh, rather than shape, is the most important lactor in insect u'ire screening. They also indicate 14 x 14 rrresh screening to be ineffective except against flies and l:rrger insects.

More than 7,000 live mosquitt-res were employed in 167 separate tests clesigned to explore insect reaction to all conceivable atmospheric, temperature and lighting conditions under rvhich woven wire screening would ordinarily be required to furnish protection.

The university research is now completed, but another phase of the program, in which the rigidity, strength and other physical properties of various mesh sizes are being studied at the l'ittsburgh Testing Laboratory, is still in progress.

The research had its inception in April, 1945, when the armed services instructed the wire screening industry to produce nothing but 18 x 14 mesh, as a substitute for 18 x 18 and 16 x 16 rnesh. In June, 1945, the War Production Board issued an amendment to Limitation Order L-303. stipulating that on and after July 1, 1945, only 18 x 14 mesh wire screening could be produced for either civilian or military use.

These directives were predicated on calculations that the change yguld increase production without necessitating any increase in. Skilled manpower, which was at that time and is still d prime factgr in the industrial picture.

While complying in full with these emergency orders, the wire screening producing industry re,cognized the need for more scientific information on the subject than was then available, and set up a special budget to underwrite impartial studies of the relative protection furnished by the mesh sizes in question.

Contracts were entered into r'vith the two universities

Insect \X/ire Screening Bureau

and lvith the independent testing laboratory for a series of closely controllecl tests .l,r,hich would be as critical as human ingenuity could devise, and rvhich rvould be entirely impartial.

'fhe tests lvere concentratcd on 18 x 18, 18 x 14 zrncl 16 x 16 mesh sizes of electro galvanized steel and commercial bronze insect wire screening; about 6,000 mosquitoes being used in 123 tests of these three sizes. The remaining tests u'ere divided a.nrong 14 x 14 mesh and :t few other sizes and shapes.

Since the smallest species of mosquitoes could be expected to yield the most critical determinations with regard to respective efficiencies of the mesl-r sizes being studietl, Aedes aegypti, the yellow fever mosquito, was used in great numbers. It is one of the smallest mosquitoes common to the United States. Although tl.re malaria mosquito, Anopheles quadrimaculatus, is cor.rsiderably larger than Aedes aegypti, it was also used, because it is extremely prevalent in many sections of the country.

Actual results of these tcsts, summarized. briefly, showed that an average ol 3.6/o of rnosquitoes confined in specially constructed cages \l'ere able to get through 18 x 18 mesh screening; 24.7o/o escaped through 18 x 14 mesh; and 24.9/o escaped through 16 x 16 mesh.

Efforts of wire screening producers in recent years to discourage the sale of l4 x 14 mesh were supported bv the "escape" figures for that siz.e: 55/o of the mosquitoes confined in 14 x 14 mesh cages, were able to get through.

The voluminous statistics furnished by the universities prove that 18 x 14 mesh is not comparable to 18 x 18 mesh in protective efi6ciency. It is, however, definitely on a par with 16 x 16 mesh, and it is accordingly evident that size is more important than shape in the effectiveness of any mesh.

Complete details of the tests at the University of Florida and the University of Delaware, together with the findings of tl-re Pittsburgh Testing Laboratory, will be made public 'ivhen all of the ll'ork now under way has been completed.

Sacramento Club Hears Talks On Veteran Rehabllitation

The regular monthly dinner meeting of Sacramento HooHoo Club was held at Wilson's Restaurant, Sacramento, on Wednesday evening, Ianuary 16.

Ray Burdg, Noah Adams I-umber Co., Clarksburg, California, president of the club, presided.

W. Henry Gilbert, Sierra ttill & Lumber Co., Sacramento, introduced the speakers.

Rodney Richardson, UCLA graduate, rvho lvas in the Marine Corps during the war, and is now executive secretary of the California Veterans' Commission, a State organization, tvas the first speaker. He was follorved by Dr. T. A. Pasto, veteran of the Army Air Forces, and norv veterans' administrator at Sacramento Junior College. They both told horv their organizations are helping veterans of \\''orld War II to get back into civilian jobs, and also discussed the selective placement of disabled men.

The talks rn'ere follorved by many questions. Those who asked questions included the follorving: W. Henry Gilbert; Les Carr, W. A. Pefley, Charles Shepard, Ray Burdg, LeRoy Miller, and William Lothrop.

The attendance was about fifty. Monthly meetings held on the third Wednesday of each month, C. D. Master is secretary.