Eggs on new water lily

Asked July 5, 2017, 10:09 AM EDT

We recently set up a frog pond and put in an Attraction Water Lily, and have started seeing what looks like an egg case under several of the lily pads. I've been removing pads that turn yellow along with the spent flowers. Are these beneficial, or should I try to remove them ?

Baltimore County Maryland water lily

6 Responses

We think this might be rat-tailed maggots, but we have submitted your photos to another expert for a second opinion. We will be in touch again soon, once we hear back from them.


Those pictures from my iPad weren't very clear - maybe these from a real camera are better. Sorry the pictures aren't in better flocus. They look like upside down dixie cups and have a tough texture.

Thank you for the additional photos. I will pass them along to our entomologist to take a look. We'll get back to you soon.


We had entomologists at the MD Department of Agriculture look at your photos. These look like egg cases of a Tropisternus beetle, in the family Hydrophilidae. They are predatory and beneficial.

They said "very cool!" -- and they wanted to see if you would be willing to send them some samples to look at. Just one or two in a little bottle of rubbing alcohol would be sufficient. If you are willing to send a couple samples, here is the address:

Maryland Department of Agriculture /PPWM
Attention: Gaye Williams
50 Truman Pkwy
Annapolis, MD 21401

Please reference Ask an Expert Question #411828. Thank you.


Oh - these are the black beetles that zip around in the pond ! They showed up within a couple days of the new pond being filled with water.
I can send you a couple of these egg cases, but I'm going to be much more careful in removing the yellowing lily pads so as not to take any more !
Thanks so much !