The only detailed trapping experiments I am aware of were done with tsetse in Kenya (Brightwell et al., 1991). These authors compared catches in NG2G traps with cones made from different kinds of netting or thin cloth relative to a standard trap with white nylon netting. Catches were mostly related to the amount of light transmitted. Hence, catches were low with slightly opaque cloth, and high with light netting, or netting with a wide mesh. I have obtained similar results for biting flies in Canada. I have also found that catches of some species are highly sensitive to the balance of ultraviolet versus visible light [unpublished].

These values may differ from manufacturer's specifications. Spectral transmission data are available for many materials, along with colour indices at Research Resources.

Economical traps can likely be made with most insect screening or mosquito netting intended for outdoor use, so long as it is not too dark. For many species, there appears to be a benefit in the use of white netting.

Note that white netting often contains optical brighteners, and hence, is fluorescent. Ultraviolet protectants are also used, so transmission of ultraviolet light as opposed to visible light may vary among similar products. Additives, as well as fabric finishes, may also change without notice as retail suppliers respond to market supply and demand (most netting is made in Asia). These fine details may be important, given the sensitivity of biting fly vision to both polarized light and to ultraviolet light.

84, 55% Fine mesh white polyester mosquito netting, about 529 holes per square inch, Type IN-06 from Barre Army/Navy in Vermont, USA (2003)
Economical netting that lasts for about two seasons, see Mosquito Curtains below for a more robust option in outdoor netting

81, 56%, Typical mesh white polyester mosquito netting, about 196 holes per square inch, Type IN-01/02 from Barre Army/Navy; this netting becomes fragile after just one season

82, 57%, White polyester mosquito netting, about 480 holes per square inch, from an entomological supplier in California, USA
Type 7250A from Bioquip

80, 67%, Grey "No-seeum" netting, about 625 holes per square inch, very fine weave retains biting midges such as Culicoides (similar material sold as IN-08/09 by Barre Army/Navy), numerous retail sources

61, 61%, Olive drab mosquito netting, about 196 holes per square inch, Type IN-05 from Barre Army/Navy, typical material in bug jackets, head nets and tents

60, 60%, Green polyester netting, about 480 holes per square inch
Type 7250B from Bioquip, very similar to olive drab netting above

65, 66%, Black aluminum window screening, about 288 holes per square inch,  New York Wire, highly transparent but shiny, cannot be sewn, but could be useful for applications where birds attack netting

58, 58%, Charcoal fibreglass insect screening (vinyl coating on fibreglass), about 225 holes per square inch, Bay Mills, typical material in windows, doors, porches, many similar products, e.g. in lighter grey

Heavy-duty Furniture Mesh

I have tested  a semi-opaque Nzi trap made entirely out of blue, back and white mesh. This all-mesh trap caught many tabanids, and hence may be useful in a windy or dusty environment. Unfortunately, it was a very poor trap for stable flies.

Practical Advice

Whatever you choose, it should be highly-transparent and uv-protected

Insecticide-impregnated mosquito netting is almost surely useful, but I am unaware of any tests with biting fly traps. Detailed information on WHO-approved options can be found at the World Health Organisation. Impregnated bed nets for malaria prevention are a potential source of materials, but are not yet approved by the PMRA in Canada (HealthBridge). Material in bed nets may be too fragile for prolonged outdoor use. Insecticide-impregnated clothing is now also vailable in the USA at Buzz Off Insect Shield. This area is a rapidly developing field.

86, 68%, VF white polyester mosquito netting (2003), 12 x 13 mesh, 156 holes per square inch, typically impregnated with deltamethrin for use in bed nets for malaria prevention, see details of Permanet ® 2.0 in Mesh Sizes

89, 70%, VF white polyester mosquito netting (1997), 9 x 9 mesh, 81 holes per square inch, used extensively for all kinds of tsetse traps in the late 1990's by many researchers - Vestergaard Frandsen A/S

86, 64%, White polyester mosquito netting (1996), 15 x 20 mesh, 300 holes per square inch, used at CIRDES in Burkina Faso in West African tsetse traps in the late 1990s, purchased locally
Ouagadougo, sample from Sandrine Amsler-Delafosse

60, 61%, VF black polyester mosquito netting (1997), preferred over white by some tsetse researchers in the 1990's, e.g. for F3 or Epsilon traps
Vestergaard Frandsen A/S

65, 64%, Fine black synthetic netting, used as transparent inserts in the very first electrocuting nets developed in the 1970s in Zimbabwe, sample from John  Hargrove obtained in the 1990s

48, 46%, Black synthetic netting, used as inserts in electrocuting nets supplied by Bonar Industries in Zimbabwe in the 1990s to tsetse researchers, rather opaque netting, unknown source

63, 46%, Light brown 32-mesh Saran® screen (PVDC), used in Canopy traps for tabanids in USA, sample from Lane Foil (1996)
Chicopee Manufacturing, Gainesville, Georgia