Brick walls, as they age, often get mortar holes. These holes are easy to access to come kinds of wasps that are the right size to fit in. These same wasps can enter through plastic roof vents, any opening in a roof, wall, under a deck, in an old rodent burrow or even in your wall or attic. The most common wasp to do this is the yellow jacket as they are very small, some of the smallest wasps in Ontario. They can easily fly into weep vents, fascia vents and mortar holes, queens as well and they can start a nest and grow their workers in the safety of your wall.
It’s hard to notice a first, the wasps act very nonchalantly coming out only one at a time and with long breadths between. This is because they are trying to both build a larger nest, set down the queen’s new larva in nest pods and hunt for insects with their stingers so they can decapitate them and feed them to the larva so they can transform into adult wasps. The adult wasps are all sterile females and cannot mate. This is good for getting hard work done quickly. When the autumn arrives the queen will cease making workers and begin the process of birthing larva that will grow into sexually active new queens and sexually active males. The males die immediately after mating. The females fly off to hibernate with their eggs and then come back out in the early spring to make a pocket nest and produce workers. This is the best time to deal with the nest, it will be small and likely easy to destroy. Only one wasp is tending it
There are a lot of different types of wasps and hornets, which are wasps but do look different and are often large and black or blue. Finding out what kind of wasp nest you have can define whether or not you need to remove it. Yellow jackets are famous for their vicious aggression and are considered one of the most severe types of wasp infestations you can have in North America. Yellow jacket wasps tend to live almost anywhere, unlike most wasps that stick to holes or trees or roofs overhangs the yellow jackets specifically seek out human homes knowing they will have plenty to eat. They tend to build open nests either in abandonment rodent burrows or in enclosed spaces like an attic or the inside of a wall. While they are more than capable of making an enclosed nest like hornets they seem to prefer making them in safer less open areas likely because of their small size. If one gets into your home through a best or hole in the mortar DO NOT SEAL THE HOLE. This will not kill the wasps. They will continue to survive but will be unable to access food. This is an issue they can resolve and the way they do it will terrify you. They will start chewing through your drywall, remember, they make nests by chewing wood so drywall is nothing to them. They will enter your home and swarm your food and attack you assuming you are the one who locked them in their nest. This is because wasps are smarter than most other insects. They can recognize the faces of humans animals and other insects and if you harm them they will hunt you around corners, avoiding other people and around obstacles to the point that they will wait for you over water for you to come up for air. Hornets are also dangerous but rarely enter a house in that way. There are other types of wasps like mud Daubers who make mud nests on walls and trees and paper wasps who make open nests that look like a gramophone horn. These are not as much of a threat but the yellow jacket can endanger your life so call a professional wasp remover and do not seal the entryway.