Elm Seed Bug

Identification & Biology
Latin Name : Arocatus melanocephalus
Category : Insects & Spiders
Description :
  • Adults are 6.5 – 7 mm (about 1/3 inch) long
  • Black and rusty red colour with black triangle bordered by a rusty coloured triangle on the back 
  • The outer margins of the abdomen have contrasting black and white bands 
  • Immature stages (nymphs) have a black head and a red abdomen; older nymphs have wing buds and two black spots on the back of the abdomen 


The life cycle of Elm Seed Bugs in British Columbia has not been determined. In Europe and the United States, it has one generation per year. Elm seed bugs overwinter as adults in and around structures and emerge in the spring to lay eggs on elms. Nymphs feed on elm seeds from May-June and adults are present in the summer. There are five immature stages and because of the long egg laying period, life stages may overlap with adults and immature stages being present in June and July. 


Elm seed bugs live on elm trees in residential areas. The bug is native to Europe and the Mediterranean region. Kelowna was the first reported location in Canada in 2016, with additional reports of infestations by homeowners in 2017.  

Impact & Risks
  • Elm seed bugs feed on elm seeds and leaves but do not cause much damage to the trees. They are not known to feed on agricultural crops.  
  • Elm seed bugs do not pose a health risk to humans or pets and do not bite.  
  • They are a nuisance when they invade homes and structures in large numbers. This can be a source of discomfort and anxiety for homeowners. The bugs stink when crushed and their fecal droppings on structures are an eyesore. 
Prevention & Mitigation
  • Prevent entry into homes or buildings by sealing off any access points in windows, doors and screens. 
  • Remove and prune elm trees to reduce food source for elm seed bugs. 
  • Clean up elm seeds and debris around the home and structures. 
  • Inspect firewood for overwintering adults before bringing into the home. 
Treatment & Disposal


  • Vacuum bugs in and around homes. For large numbers, use a shop vacuum with 1-2 inches of soapy water in the bottom to drown the bugs.  
  • Use sticky traps for trapping bugs around window sills. 
  • The use of insecticides for controlling seed bugs in the home is not recommended. 
  • For high numbers, treating immature stages outside the home with a barrier spray along foundations, patios, doors and windows will help prevent bugs from entering homes.  
  • Products registered for home use containing permethrin, carbaryl and malathion will provide control. 
  • Homeowners can hire a commercial pesticide applicator for more control options. 
Okanagan Distribution

Priority Level Definitions

Watch For - Poses a significant threat (very high risk) and does NOT presently occur in the region OR is relatively new to the region and is very limited in extent.
High - High risk/impact; limited population with significant potential to spread in the region.
Medium - Medium risk/impact; limited distribution – broader population distribution with potential to spread further in a region.
Low - Low risk/impact; may be widespread or not, may be of concern in specific situations with certain high values – e.g. specific agriculture crops. Some species may be treated primarily with biological control agents.