Ootheca

Question: What is this foamy looking thing I have found in my tree?

Answer: This object is an ootheca, (or egg case), deposited by a species of praying mantid. The ootheca is a system used by a number of invertebrates, including many molluscs and a number of the insects such as cockroaches and praying mantids. The mantids lay the eggs into a foamy protein which hardens and forms a protective case, while the ootheca of cockroaches is usually covered by a thin layer and often looks like a small purse or pod.

Cockroaches and mantids differ in their use of the ootheca in that the mantids usually deposit their oothecas on vegetation or sometimes a surface like a wall or brickwork, while many species of cockroach carry the ootheca around attached to their abdomen, (others have the ootheca held inside the body).

The ootheca of the praying mantid is often characteristic of the species and can hold from 10 to 400 young. The young can take from 3-6 months to emerge. If you find a mantid ootheca some people are tempted to take them inside to try and see them hatch. This may not be the best thing for the young mantids as the warmer conditions in the house can cause the young to hatch earlier than they should and if there is insufficient food the young nymphs may eat each other. The best thing is to leave it where you find it and observe it as we move into spring and see if you can observe the young emerge. Praying mantids are great to have around the garden as they consume numerous insects and are fascinating to watch.