Decomposing animal studies were carried out during a period of 30 days following animals' death in summer , autumn and spring. Winter test was undertaken for a 120 day period.

Study dates and seasons:

The field study was conducted on a farm located placed near Esplús (Huesca), 281 meters high over the sea. The carcasses were exposed simultaneously in two different sites:

EXPOSED, UNSHADED AREA:

Two pigs labelled as pig 1 (P1) and pig 2 (P2) were placed at a fenced site, without trees. The animals were separated each other 10 meters, located at a fenced area and exposed to direct sunlight,.

SHADED AREA

Two pigs labelled as pig 3 (P3) and pig 4 (P4) were placed at 300 meters far from the ones in the exposed area and 10 meters between them. The predominant vegetation surruonding the place consisted of Populus tremula and pseudoacacias (Gleditsia triacanthos). Shrubs such as the Rubia tinctorum and brambles (Rubus ulmifolius).

Sixteen pigs Sus scrofa (L.- hybrid between LandracexLarge White), hogs and sows, 8,500 to 13,100 kilograms weight were used for the experiment.

At each site the carcass was protected from large animals by a metal cage 90x70x45 cms, covered with a metal wire mesh containing 1,3 cm wide squares in order to allow arthropods to reach the corpse but prevent large scavengers such as wild dogs from accessing it.

The four cages used were made with four legs 25 cms long, each of them inserted into metal tubes previously fixed in the concrete floor in order to lift the cage and keep it in its original position.

The pigs were killed inside their cages by a shot to the front of the head. A layer of river sand, 10 cms thick was placed under each cage to achieve larvae reach puparial stage near the pigs.

Arthropods were collected using a hand net and different specimens obtained employing paintbrushes moistened with 70% alcohol and using ethyl acetate. They were preserved in entomological boxes or in test tubes containing 70% alcohol.

Larvae were preserved in 70% alcohol during a maximum of 24 hours. Afterwards each sample was measured, classified taxonomically and mounted on glass slides.

Each specimen was identified with a "Ura technic" binocular magnifying glass (10 x 20 magnification lenses).

Fly larvae were prepared using Hoyer solution whose formula was described by Pastrana.

Every area was examined to detect organic material such as excrements left by animals, mainly in the shaded area placed close to the highway, to control circumstances that could give a false account of the experiment.

After weighing the pigs placed in both areas (shaded and unshaded), and killing them inside their cages, a 10 x 2 cm cut was made on the neck of each specimen in order to test if blood or soft tissue attract insects with respect to other parts of the carcass. Cages were locked and began the observation during two hours time. Corpses were checked daily.

First flies arriving and ground dwelling larvae were collected. Afterwards ten small and ten large larvae were chosen from different parts of the pigs which were preserved with 70% alcohol in test tubes. Subsequently specimens were identified taxonomically.