CO-Horts Blog

Thursday, September 27, 2018

Have You Seen These Non-Native Insects?

Posted by: Jessica Wong, Broomfield County Extension

By now you are probably aware of emerald ash borer and Japanese beetle, two invasive insects that threaten Colorado landscapes. However, these are not the only non-native insects that you should be on the lookout for. 

The Asian mud dauber (Sceliphron curvatum) is a wasp originally from areas in India, Pakistan, Nepal, Tajikistan, and Kazakhstan. It is not a garden or agricultural pest, but all non-native species have the potential to disturb an ecosystem. The distribution of Asian mud dauber in North America currently includes Quebec, Ontario, and now Colorado. Within Colorado sightings have been reported in El Paso, Douglas, Denver, Larimer, Mesa, and Boulder Counties. It is likely that these wasps are in more than just these six counties, which is why we need your help finding them.

A female Asian mud dauber. Photo credit: Whitney Cranshaw
Female Asian mud daubers build nests out of mud along elongate crevices. In the Front Range they have been seen using the edge of windows as nesting sites. They hunt for spiders, which are put into the nests to provision a single larva. Asian mud dauber can be mistake for the closely related black and yellow mud dauber, an insect that is established and found throughout Colorado.    

Asian mud dauber nests in a window frame. Photo credit: Betty Cahill
The next non-native insect you should watch out for is a leafminer of Siberian elms originating from China. The insect is a small moth currently known only by its scientific name, Stigmella multispicata. It has become widespread across the eastern part of North America since it was first found in 2010. It is possible that Stigmella multispicata is already in Colorado.

Leafmines made by Stigmella multispicata larvae. Photo credit: Daniel Gilrein
The larvae of this moth are tiny green caterpillars. These caterpillars create snake-shaped leafmines that get progressively wider as they grow. Once the larvae are fully developed, they exit the leafmine, spin a line of silk and drop to the ground where they will pupate. The leafmine pattern, the size and color of these caterpillars, and their use of silk are characteristics that distinguish this leafminer from the other elm leafmining insects established in Colorado, such as the European elm flea weevil or the elm leafminer.

Stigmella multispicata larvae. Photo credit: Daniel Gilrein
If you see any signs of Asian mud dauber or Stigmella multispicata, take pictures and send them to CSU entomology professor, Whitney Cranshaw, at, and don’t forget to tell him what county you saw the insects. 

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