December 1, 2015
by Richard Smart
"What is that?” That was the question I asked my supervisor, Lila Higgins, back in the fall of 2012 when she brought in a strange looking object attached to a stick. “This is an ootheca, an egg case” she replied.
The ootheca was attached to a stick that Lila had brought inside to our office. Lila saw the stick lying on the ground in our Nature Gardens. Originally, she was going to place the stick into a nearby garden bed, but as she looked closer she noticed the ootheca. She recognized the shape of the ootheca to be that of a mantid egg case. Lila decided she would help the mantid babies by bringing them indoors, so they could develop without interference from predators or people.
I was very curious on how long it would take for the mantids to hatch out, and I wondered just how many and how large the young mantids would be when they emerged.
Days of checking the ootheca, turned into weeks, which turned into months. Then finally, in March of 2013, I heard Lila happily exclaim, “The ootheca hatched!” I ran over and was fascinated to see miniature mantids on her desk. They looked like the much larger mantids I was used to seeing, but teeny tiny. They were unbelievably cute. Lila even wrote her own blog post about it.
That experience made quite an impression on me, and it came to mind recently when I saw an ootheca attached to a Lion’s Tail plant in the Nature Gardens at NHMLA. My colleague, Richard Hayden, also recently posted an ootheca to Instagram, and that got me thinking that others were likely seeing these in L.A. and perhaps they didn’t know what they were.
An ootheca can blend in very well with the plant they are attached to, so many people may not see them. Or people may think they are a sign of a sick or injured plant, and may remove the branches they are attached to, not realizing they were removing baby mantids from their gardens. Mantids are considered to be a beneficial insect since they will eat many garden pests such as grasshoppers, caterpillars, and aphids – you want mantids in your yard. The egg case actually starts as a frothy mass, but hardens to form a tough capsule that protects the growing young inside. Depending upon the mantid species, there can be anywhere from dozens to hundreds of mantids inside the ootheca, so by picking up sticks with an ootheca attached to them can help out a lot of mantids.
Are you seeing oothecae in your part of L.A.? If so, I encourage you to let them be. The egg case will protect them from rain and temperature changes. If you see an ootheca attached to a broken stick laying on the ground then kindly place the stick in an area where they are less likely to be damaged by people. You can also take photo of the egg cases, and tag us using #NatureinLA so we can add your #ootheca photos to our L.A. Nature Map!