**2.1 Invertebrates**

Insects and other invertebrates live within their own microclimes and just a small change in position can affect their TB. Some species of ants, for example, move between nest areas during seasonal changes or use objects such as leaves or rocks to alter their insulative properties. Fire ants are able to raise their nest temperature by modifying their nest shape relative to the sun's angle, while wood ants use solar radiation in combination with behavioral modifications to maintain ideal nest temperatures (Vogt et al., 2008; Galle, 1973). Non-communal insects such as grasshoppers bask to increase their TB (O'Neill & Rolston, 2007). Butterflies in general often bask or use ground contact to gain heat by conduction and convection then seek shade or minimize their exposed wing surface area to either facilitate heat loss or decrease heat absorption (Clench, 1966). Basking monarch butterflies take to the air during periodic cloud cover before returning to their clusters (Calvert et al. 1992). The lack of direct sunlight is enough for them to expend energy, creating heat through movement of their body. The difference in temperature from direct solar radiation to cloud cover likely stimulates this adaptive response in butterflies, causing them to return to the safety of the colony in the chance that any sustained cloud cover could lead to lower thoracic temperatures during migrational flight (Calvert et al., 1992). Several species of Arctic butterflies select specific basking substrates and orient their wings perpendicular the sun, allowing them to absorb heat in order to continue locomotion even at very low TA (Kevan & Shorthouse, 1970). Without the ability to maintain their threshold temperature during flight, stranded butterflies could be subjected to increased predation and risk exposure to cold stress.

Honeybees use solar radiation at TAs under 30°C, the minimum thermal threshold, as an alternative to generating energy to raise thoracic temperatures. Relying on solar radiation to increase TB enhances muscle efficiency during flight and allows the bees' suction pump to function at low TA. If overheating occurs, bees actively seek water to ingest, using the liquid to cool thoracic temperatures (Kovac et al., 2010). Other insects such as wasps also use solar radiation to increase thoracic temperature so their own active production of heat is reduced (Kovac et al., 2009).

Insects are not the only invertebrates to be affected by solar radiation; those living within the intertidal zone of oceanic coastlines are subjected to solar rays as well. Although many organisms can avoid direct solar radiation by moving to safe hiding places between rocks, in tide pools, or in the sand via burrowing, others are limited in their ability to use locomotion to do so. For example, marine snails will flee from areas exposed to direct solar radiation and move to cooler areas close by often in shade or under the waterline (Chapperon & Seuront, 2001). Periwinkles are unable to flee the declining water level and are thus equipped to withstand relatively short periods of desiccation and thermal stress. In fact, they often orient themselves frontally or dorsally facing the sun to limit the amount of sunlight hitting their lateral surfaces. By reducing the surface area perpendicular to the radiation, periwinkles can maintain a lower TB when subjected to the desiccating heat and solar intensity during low tides (Muñoz et al., 2005).

#### **2.2 Amphibians and reptiles**

Small amphibians and reptiles must be careful to maintain a certain TB and are often affected by microclimate changes. It is well known that ectotherms use basking to supplement heat gain, making solar radiation an important thermoregulatory tool (Nagy,

during seasonal changes or use objects such as leaves or rocks to alter their insulative properties. Fire ants are able to raise their nest temperature by modifying their nest shape relative to the sun's angle, while wood ants use solar radiation in combination with behavioral modifications to maintain ideal nest temperatures (Vogt et al., 2008; Galle, 1973). Non-communal insects such as grasshoppers bask to increase their TB (O'Neill & Rolston, 2007). Butterflies in general often bask or use ground contact to gain heat by conduction and convection then seek shade or minimize their exposed wing surface area to either facilitate heat loss or decrease heat absorption (Clench, 1966). Basking monarch butterflies take to the air during periodic cloud cover before returning to their clusters (Calvert et al. 1992). The lack of direct sunlight is enough for them to expend energy, creating heat through movement of their body. The difference in temperature from direct solar radiation to cloud cover likely stimulates this adaptive response in butterflies, causing them to return to the safety of the colony in the chance that any sustained cloud cover could lead to lower thoracic temperatures during migrational flight (Calvert et al., 1992). Several species of Arctic butterflies select specific basking substrates and orient their wings perpendicular the sun, allowing them to absorb heat in order to continue locomotion even at very low TA (Kevan & Shorthouse, 1970). Without the ability to maintain their threshold temperature during flight, stranded butterflies could be subjected to increased predation and risk

Honeybees use solar radiation at TAs under 30°C, the minimum thermal threshold, as an alternative to generating energy to raise thoracic temperatures. Relying on solar radiation to increase TB enhances muscle efficiency during flight and allows the bees' suction pump to function at low TA. If overheating occurs, bees actively seek water to ingest, using the liquid to cool thoracic temperatures (Kovac et al., 2010). Other insects such as wasps also use solar radiation to increase thoracic temperature so their own active production of heat is reduced

Insects are not the only invertebrates to be affected by solar radiation; those living within the intertidal zone of oceanic coastlines are subjected to solar rays as well. Although many organisms can avoid direct solar radiation by moving to safe hiding places between rocks, in tide pools, or in the sand via burrowing, others are limited in their ability to use locomotion to do so. For example, marine snails will flee from areas exposed to direct solar radiation and move to cooler areas close by often in shade or under the waterline (Chapperon & Seuront, 2001). Periwinkles are unable to flee the declining water level and are thus equipped to withstand relatively short periods of desiccation and thermal stress. In fact, they often orient themselves frontally or dorsally facing the sun to limit the amount of sunlight hitting their lateral surfaces. By reducing the surface area perpendicular to the radiation, periwinkles can maintain a lower TB when subjected to the desiccating heat and

Small amphibians and reptiles must be careful to maintain a certain TB and are often affected by microclimate changes. It is well known that ectotherms use basking to supplement heat gain, making solar radiation an important thermoregulatory tool (Nagy,

exposure to cold stress.

(Kovac et al., 2009).

solar intensity during low tides (Muñoz et al., 2005).

**2.2 Amphibians and reptiles** 

2004). Turtles will often choose habitats with access to direct solar radiation and bask on sunny days (Dubols et al., 2009). Ectotherms will frequently expose a maximum amount of surface area toward the sun, regulating the interception of solar radiation through body orientation. Some reptiles have dark patches to aid in heat absorption. Certain species of lizards orient their bodies either parallel or perpendicular to the sun's rays based on TA. Lizards living in high altitudes increase basking frequency, are more likely to orient perpendicular to the sun, and restrict durations of activity to minimize the range of temperatures to which they are exposed (Adolph, 1990; Hertz & Huey, 1981). However, this can raise their chances of being captured by a predator. Kestrels in Norway return to their nests with an increasing amount of lizards, which typically peaks in midday. Solar intensity, as well as TA, often influences the abundance of lizards available to kestrels due to possible patterns in lizard behavior (Steen et al., 2011). The giant tortoise from South Africa is another species known to orient itself based on solar radiation. When facing away from the sun, the carapace casts a shadow on the head and neck area allowing the tortoise to inhibit the rate at which its TB increases. This maintenance of a larger thermal gradient between the skin surface and TA allows the tortoise to forage for longer periods under direct solar radiation (Coe, 2004). Some species of toads living at high altitudes are more active on sunny days, raising their TB by 20° or more in some cases (Lambrinos & Kleier, 2003). Heat gain using solar radiation also aids in digestion and increases growth rates of toads and other anurans at both extreme and moderate elevations. When food is withheld, toads end basking and allow their TB to decline (Lillywhite et al., 1973). Dependence on solar radiation makes it possible for most species of reptiles and amphibians to live at high elevations in tropical regions.
