If your potted plants are looking a little sorry right now — wilting, new growth shriveling or a general lack of unhappiness — it could be short winter days or dry heat. Or it might be minuscule troublemakers: spider mites. These tiny creatures, less than a millimeter in size, are not easily seen. The best way to check for them is to examine the plant in a sunny window or a strong backlight. If you see fine webbing, especially in the crotches of the stems or on new growth, it’s a sure sign your plant is under attack. The mites suck on the plant sap, causing stilted new growth and deformed leaves. Infested plants will start to turn brown. If left unchecked, mites could destroy a whole houseplant.