Published in the McAllen Monitor, January 7, 2023
Story and photos by Anita Westervelt, Texas Master Naturalist
Many insects do not function at temperatures below 50 degrees Fahrenheit.
Insects, spiders and other garden creatures shelter in a variety of places during cold weather, like rock and wood piles, under garden debris, compost piles and leaf litter, in spent plants, dense shrubbery, crevices around structures, even behind the bark on trees.
In our South Texas climate, insects will be active on warm days and inactive on cold days. But when temperatures plummet to freezing, other measures come into play. For instance, some insects can rid their body of all food and liquid so that ice can’t form inside the body and kill it. Some beetles survive by entering diapause, an inactive state where an insect ceases development and experiences metabolic slowing. Many adult insects, like the Texas unicorn mantis and longhorn beetles will have laid eggs and died by winter but their larvae will overwinter in protected areas.
Some insects produce an antifreeze of sorts in their bodies or blood – a biological change that keeps ice crystals from growing or that lowers the temperature the insect’s blood will freeze. Another defense is freeze tolerance, where the insect body freezes solid and thaws out when it warms up.
Spiders’ bodies produce glycol compounds that also function like an antifreeze and protect their tissues from freezing. Spiders go through a biological cold-hardening process and also enter diapause; their bodies slow down but they are able to emerge on warmer days to hunt for food. Many spider species, like orb weavers, mate and lay eggs then die before winter; female spiders lay eggs in hidden places or create nest-like webs to protect their eggs.
Bees group together in the hive, keeping it warm and staying alive by eating their honey stores; ground nesting bees go to ground. Flies don’t survive freezing temperatures; most common flies can’t hibernate but hide where they can access food in sheltered areas. Many bugs bury themselves underground.
Lizards and snakes brumate, a state of inactivity or torpor, which involves a lower-than-normal body temperature and lowered breathing, heart and metabolic rates; it is triggered by ambient temperature and food availability.
Some birds also enter short-term torpor where they require less food. Perching birds fluff their feathers to trap heat and slow metabolism; shivering creates additional heat from circulation and muscle movement. Birds of a species find a wind break and huddle together to share warmth. At night, birds gather together in thick shrubs, or squeeze together on tree branches that block the wind.
Birds of all sizes alternately stand on one leg and tuck the other leg under their belly to keep it warm or hunker down, covering their legs and feet with their warm bodies and tuck their head under their scapular feathers to conserve heat by breathing air warmed by their body.
Ducks, gulls and wading birds have a built-in heat-exchange where the arteries with hot blood running to the feet pass right next to the cold blood running in the veins back to the body.
- 30 -
Sidebar
Step away from the pruners
– Opt for creature refuges over aesthetics
Story and photos by Anita Westervelt, Texas Master Naturalist
Freezing temperatures and sustained damaging cold winds may have left shrubs and trees in various states of seeming disaster but don’t begin removing dead looking leaf stalks, branches and limbs just yet. The danger of another freeze may be in the wind, and although leaves are dry and crinkly, the branches may still be healthy. Even dried vegetation can offer a modicum of protection to a plant and surrounding vegetation should another bout of winter weather visit the Valley.
Watering cold-shocked and wind-battered plants may help them rehydrate but don’t fertilize just yet. When working in the garden, think about the critters and not the aesthetics. If you collect grass clippings when you mow, combine them with raked leaves and spread them thickly throughout your native nectar and pollinator gardens. If you compost, the top layers may still be in a state where they can be useful as mulch around plants or on top of emerging plants for protection and critter refuge.
If the strong winds produced a lot of sticks, collect them, and push small bundles under shrubs and other out of the way places for insect hideouts. Thicker downed branches, if you have the means, may be cut and tucked under large shrubs and left to decay, which will provide good bug habitat all year.
Many native plants, shrubs and trees survived recent freezes better than exotic and cultivated species. Berlandier’s fiddlewood, Citharexylum berlandieri, may have partially cold and wind burnt leaves, but the buds and blooms are attracting flies, ants and some wasp species for nectar.
Winter blooming plants are important for the warm winter days when insects are about. Species able to survive short bouts of freezing temperatures and continue blooming include tropical and scarlet sage and other salvias; native crotons; snapdragon vine, Maurandya antirrhiniflora; pink mint, Stachys drummondii; American germander, Teucrium canadense; velvet lantana, Lantana velutina; Trixis, Trixis inula; scorpion’s tail, Heliotropium angiospermum; and Turk’s cap, Malvaviscus drummondii.
For a list of books about native plants, handbooks and planting guides for Rio Grande Valley plants and a list of local native plant growers, visit https://www.stbctmn.org/post/valley-native-plant-growers-nurseries.
- 30 -