Study of the "G. liparidis" showed almost 90% success when the host is parasitized during premolt to the third instar. Most invertebrate predation occurred when larvae were in the litter. The population in Austria suffered high parasitism by the tachinids "Parasetigena silvestris", which may have contributed in prevention of further increase in "L. dispar" in this locality. Gypsy moth populations in different locations show vulnerability to different viral species. Nuclear polyhedrosis virus caused significant mortality in some cases. The most important pathogen is the Lymantria dispar multicapsid nuclear polyhedrosis virus (LdMNPV), sometimes referred to as NPV or "Borralinivirus reprimens". Viral particles consumed by the larva when eating through the egg chorion will kill them during the first instar. The bodies disintegrate, spreading the virus on the foliage, which will then be consumed by other larvae. Outbreaks of the virus result in high larva mortality, and the odor of the decaying larvae permeates the area. The pathogen is used as an insecticide under the name Gypchek. "Steptococcus faecalis" is another pathogen which is notable for its mortality. Larva killed by the pathogen have a shriveled appearance. "Entomophaga maimaiga" is a Japanese fungus that helps control the population of gypsy moths. It was first introduced to North America around 1910, though was not an effective control until the 1980s. Population density of larva plays a major role in their behavior. At low density, larva remain inactive during the day, but in high populations become hyperactive. Interbreeding produces deleterious genetic effects, and dispersal serves to reduces this effect. Temperature is important to the gypsy moth. Low temperatures are fatal. Temperatures of −9 °C can be withstood during the winter, an extended period will kill the larvae inside and −23 °C even for a short time is lethal. Egg deposits that are low or on the ground can be insulated against temperatures, including snow, and survive the lethal temperatures. Temperatures above 32 °C increase growth and development. Rainfall can drown larva before they are established, low populations are correlated to heavy rainfall during the larval stage. Wind is also critical to the dispersal of the larva, wind speeds of several miles per hour are enough to break the silk threads and disperse the larva.