Yes, candles can be insect repellents. Specific smells such as citronella are known to repel bugs. Citronella is a bit of a divisive smell however, and many people don't like it. There are other lovely smells out there which do the trick as well though – for example Ylang Ylang is a beautiful exotic floral. Other great options are Peppermint, Lavender, Basil, Eucalyptus, Clove and most citrus scents like Lemon and Bergamot. Sweet florals will typically entice them though!