Q: Several of these growths appeared on a shrub in my yard. Any thoughts on what it might be?
A: These are praying mantis egg cases, aka ootheca. After mating, female mantids lay their eggs in a foamy mass on trees and shrubs where their young will be close to something to eat when they emerge. The egg case, while soft at first, hardens into what you found and can contain up to 400 eggs. Mantids survive the winter as eggs in the ootheca and hatch in the spring, emerging as wingless nymphs. Mantids are predators and they require food soon after emerging. Finding none, they may begin to eat each other. So if you decide to keep your mantid eggs to watch them hatch you might want to also find a suitable food source for when they are ready. What happens this time of year is the accidental mantid colony on Christmas trees. The egg cases are often well hidden in the foliage and not always apparent when we are out selecting the family Christmas tree. If they should hatch in your house, they might be goners unless you can get them to a place outdoors where the weather outside isn’t frightful and that has a population of tiny insects.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions and photos may be emailed to firstname.lastname@example.org