The invention relates to a plastic foam bodies for use in insulation.  More particularly, the foam bodies are resistant to insect, particularly beetle, attack.  These foam bodies are especially useful in insulating farm buildings. 
Many farm buildings used to house farm animals are insulated as it allows the farmer to control the environment to which the animals are exposed.  Chicken coops and pigsties are among the farm buildings that are frequently insulated.  This insulation is credited with improving the development conditions and health of the animals, as well as keeping energy bills low.  Presently extruded thermoplastic foam boards, expanded thermoplastic bead boards and mineral wools are commonly used as insulation.  Certain insects are found to bore into the insulating material and into the wood structures of such farm buildings.  This results in the loss of insulation value of the insulation, and can result in severe structural damage to the farm buildings.  One particularly damaging pest is a beetle, Alphitobius Diaperinus.  This beetle bores into the insulation and wood structures to nest.  This beetle is also known to carry diseases which are damaging to farm animals.  Currently available insulating materials are susceptible to being bored into by such beetles. 
Representative of plastic foam materials useful in insulation boards are those described in WO 9004615 and U.S. Pat.  No.  4,085,073 (FR 2330719). 
Kagaya Japan Patent Application 58-37819 discloses a heat insulating board for barns that consists of a foamed polystyrene whose average cell size (mm) and density (kg/m.sup.3) belong in a pentagonal area (of a graph of density vs cell size) established by the points A (.70, 45), B (.40, 45), C (0.10, 65), D (0.10, 85), and E (0.70, 85) whose surface hardness is higher than 70.  The polystyrene foam boards disclosed are prepared via bubble extrusion.  The method of preparing the boards described limits the thickness of prepared boards from 20 to 30 mm.  This is disadvantageous as the insulation value of 20 to 30 mm thick board are not as high as may be desired.  What is needed is an insulation board that can be fabricated in higher thicknesses which exhibits good insect resistance. 
What is needed is an insulating material which is capable of preventing or resisting the boring of such insects into the insulating material.  What is further needed is a method of preventing such insects from boring into the insulating material in farm buildings.  What is further needed is a farm building which has insulating material which is resistant to the boring of such insects.