Insects of the Week: genus Isodontia

Isodontia elegans  carrying a paralyzed tree-cricket to provision her nest. Block 131099 on August 2, 2013.

Isodontia elegans carrying a paralyzed tree-cricket to provision her nest. Block 131099 on August 2, 2013.

Scientific name: Isodontia

Common name: Grass-carrying wasps

Family: Sphecidae

Nest type: dried grass blades

Size: 18-20 mm

Nest tunnels used: 1/2” to 5/16” tunnels

Looks like: Large rusty orange or shiny black wasps

Loosely packed grass protrudes wildly from this active Isodontia nest. (Block 131204 nest B1 on August 31, 2014)

Loosely packed grass protrudes wildly from this active Isodontia nest. (Block 131204 nest B1 on August 31, 2014)

If you’ve ever opened a window and found the tracks bizarrely filled with dead grass and bugs, it’s not the result of a strangely precise wind: you’ve happened upon the nest of an Isodontia wasp, commonly known as the grass-carrying wasps. It might be a shock to see your windows infested with insects (especially wasps!) but if you find them, don’t be alarmed. These wasps are rather un-wasplike, males completely lack a stinger and females only sting if you threaten them. Isodontia females separate their cells and plug nests with grass. They provision their cells with paralyzed, but living tree crickets or immature katydids. The wasp larvae are carnivores, while the adults feed on nectar.

Same nest as above only now with a completed packed grass nest plug. (Block 131204 nest B1 on September 2, 2014)

Same nest as above only now with a completed packed grass nest plug. (Block 131204 nest B1 on September 2, 2014)

The calendar may say October, but it has been warm enough, so you have a few more chances to go bug spotting. Isodontia are active fro mid to late summer, so you still have a chance to see them! If your windows are wasp-free, look in hollowed out tree branches, other naturally formed cavities, or your bee block. We have two species here in Colorado: I. elegans, a lovely rusty orange color, and I. mexicana, a shiny black species. Both have remarkably narrow “waist”, even for a wasp.

Cross section of an Isodontia mexicana nest showing a wasp larva feeding on provisions (tree-crickets and a katydid) in between walls of grass blades.  (Longmont, Colorado on July 2014)

Cross section of an Isodontia mexicana nest showing a wasp larva feeding on provisions (tree-crickets and a katydid) in between walls of grass blades. (Longmont, Colorado on July 2014)

DID YOU KNOW: Isodontia can produce two generations per year in Colorado. The offspring from the first generation will reuse or use nesting tunnels near their natal nests. You may have only one or two nests in July, but these can quickly multiply to five or ten nests by the first freeze. Isn’t nature great!

ADDITIONAL INFORMATION:

http://bugguide.net/node/view/5691

http://bugeric.blogspot.com/2011/02/wasp-wednesday-more-on-isodontia.html

http://ideastations.org/radio/news/grass-carrying-wasps

Advertisements
This entry was posted in 2014, Insect of the Week, Nest Plugs, Uncategorized. Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s