debris without any underlying structure. Thermoregulation Temperature extremes harm animals irrespective of whether they are endothermic or ectothermic. In endothermic animals, construction of shelters, coupled with behavioural patterns, reduces the quantity and energy cost of thermoregulation, as in the case of the Arctic ground squirrels. In ectothermic animals, moderation of temperature, along with architectural modifications to absorb, trap or dissipate energy, maximises the rate of development, as in the case of the communal silk nests of the small eggar moth Eriogaster lanestris. The primary sources of energy for an animal are the sun and its metabolism. The dynamics of heat in animal shelters is influenced by the construction material which may act as a barrier, as a heat sink or to dissipate heat. The cocoons of insect are a case in point. An interesting example is the case of silk caps which cover the pupal cells of the Oriental hornet Vespa orientalis. Firstly, the silk insulates the pupa from the air outside the cell, and secondly, it acts as a thermostatic regulator. By virtue of its thermoelectric properties, the silk stores excess daytime heat in the form of electric charge which it releases in the form of an electric current when the temperature falls resulting in heating. Cooling is aided by evaporation of excess water from the pupal cells. When the ambient temperature drops, the silk absorbs moisture and restores the moisture content by spreading water through all parts of its cocoon. Internal architectural devices, such as walls may block convection or the construction of air flow systems may cool the nest or habitat. Trap building Trap-building is a method used to catch prey instead of active hunting. Animals that snare prey will construct a trap and then wait nearby until an organism is caught. This is observed in web-building spiders, who weave elaborate webs of sticky spider silk that entangle prey. Spiders increase the size of their webs when prey are scarce, and can add extra ornamental pieces to their web in order to attract more prey. Traps can allow organisms to capture larger prey, provide protection from predators, or serve as an area for mating, as seen with spiders. Another method of trap creation is used by the antlion (Myrmeleon crudelis) larva. These larva prey on small arthropods, such as ants. The larva dig pits into fine-particle soil to capture their prey, which fall into the holes and