Many residents of the US are familiar with the box elder bug, an orange and black bug found on box elder trees in summer and found in homes in the late fall and winter as it looks for a sheltered place to spend the winter. True bugs that invade homes in summer in large numbers are uncommon. US residents may become familiar with a new species of red and black bug, the Elm Seed Bug, Arocatus melanocephalus.
The Elm Seed Bug was not considered a pest anywhere until 1999, when residents of Northern Italy complained about home invasions by large numbers of these bugs. The largest outbreaks of home invasions occurred in late May in the years 2001-2003. Every year since, invasions have been reported in different locations in Italy. Some evidence suggests that the home invasions are correlated to spells of unusually hot weather.*
Arocatus melanocephalus, the Elm Seed Bug
Like many Seed Bugs, the Elm Seed Bugs overwinter as adults, mate in spring and lay eggs on elm trees. The larvae feed on the fruits and seeds in May-June in Italy, and become adults in summer. Like most true bugs, the Elm Seed Bug has scent glands that produce a noxious odor, that deters predators. When crushed, the bugs produce an unpleasant odor.
Insects that invade homes in large numbers are prime candidates for global transport by hitchhiking in the baggage of travelers. Recently, the Elm Seed Bug has appeared in Southwestern Idaho. The bug is not expected to cause damage to Elms or have large ecological impact. Whether or not it becomes a nuisance or spreads around the US remains to be seen. The USDA/APHIS is asking the public in Idaho to be on the look out for this pest to help determine the extent of its spread.
Elm Seed Bugs Aggregate Indoors
Photo: mauriziano
http://www.naturamediterraneo.com
*Maistrello, et al. 2006. Journal of Thermal Biology. Volume 31, Issue 8, Pages 594–598.
I live in Pacifica Ca. and have observed these bugs on my property in the past 3 – 4 years. I have not seen any this year. We only see a few at a time , less than 10, Ours are black and orange, we call them SF Giants bugs
There are a lot of look alikes. You may be seeing large milkweed bugs or boxelder bugs that look similar.
I have a large elm next to my house and have had a problem with these bugs for eight or nine years now. They get into the house in large numbers and are a real nuisance, but mostly on the side next to the elm tree. Can you tell me how to distinguish them from the boxelder bug? They are definitely not Milkweed bugs. My house is on the Russian River in western Sonoma County, CA. If these are indeed Elm Seed bugs, is there someone I should contact?
Collect some of the bugs and put them in a freezer.
Take them to your county extension agent for identification.
California Dept. of Food and Agriculture or your County Dept. of Agriculture.
I live in Boise, Idaho and my house has been swarmed by this bug. I do not have Elms on my property but my neighbor does. If we spray the trees in the Spring will this help to control the numbers. I have been fighting the infestation for 3 weeks now and am about ready to move. I have sprayed the exterior three times which has helped keep the masses at bay, but they are still coming into my house-I guess through the window glides-even though I have sealed them as well as I can. Any other advice? Thanks
It is a new problem, so solutions are being tested. The vacuum cleaner is your friend.
Bugs can crawl back out the hose so empty the bag or keep it closed so they cannot escape.
An effective trap would be helpful.
I also live in Boise and even in January, I find these bugs every day on my windows and flying around the house. I have bought a small shop vac just for the purpose of vacuuming up these pests- I put a small amount of soapy water in the bottom of the shop vac so they will drown! They leave their marks on the windows and the house siding. Why are they active even in winter? We have had a spell of very cold weather (-5 º F) and it did not seem to stop them at all. How are they staying alive in the winter since they feed on elm seeds?
What is an effective trap?
Good idea with the shop vac. Their metabolism slows in the winter and they can go long times without eating.
For some brown marmorated stink bugs, people cut the top off a 2 liter soda bottle and invert it to make a funnel into the bottle. Duct tape the top to the bottom. A cheap batter led light attracts stink bugs in the dark, like a closet or attic. I don’t know if it will work on these elm bugs.
Soapy water in the bottom of the shop vac is a good idea.
Thanks for your reply and the idea of the soda bottle funnel! I will try it.