WSU Extension

Hortsense

Predatory Flies
 
Bee flies 
Dance flies 
Hover flies 
Long legged flies 
Predatory midges 
Robber flies 



print version| pdf version| email url    
Caption: Adult hover fly (Sphaerophoria sp.) (Syrphidae)
Photo by: D.G. James
  
Predatory Flies : Hover flies
(revision date: 10/11/2018)


Biology
Superficially, hover flies do not look like ‘flies’, instead they resemble wasps by having a yellow or orange and black-banded abdomen. They range in size from ¼ to ½ inch and mimic stinging wasps and bees, which presumably confers survival benefits to the stingless hover fly. Such is the cleverness of their deception that agricultural fields have been sprayed because of the presence of ‘wasps’! Before you beat a hasty retreat from that ‘wasp’ in your garden observe it a little closer… Is it hovering? Most wasps do not spend time hovering, but hover flies excel in this behavior. Hover flies frequently visit flowers feeding on nectar and pollen (belying their other common name, flower flies) and are important pollinators. The larvae of hover flies are ¼ to ½ inch long, green, gray or yellow and legless. They develop for 1-2 weeks feeding voraciously on aphids, thrips, mites and other small insects. If you find a legless maggot within a colony of aphids, this will be a hover fly larva.

Prey or Pest Targeted
  • Mites, aphids, scale insects, thrips, caterpillars, beetle larvae, flies, wasps, grasshoppers, bees
     
Attracting and Keeping Natural Enemies & Pollinators in Your Yard
  • Avoid regular use of synthetic, broad-spectrum pesticides. Infrequent use of certain narrow-spectrum pesticides is more compatible with some beneficials but generally the less chemical inputs there are, the greater and more diverse the beneficial insect community will be. Extensive lawns are also not conducive to attracting and retaining a diversity of beneficial insects, mites and spiders. Minimize lawn areas and maximize shrub and bush plantings. Many beneficials reside naturally in riparian and other ‘natural’ areas near to many back yards. Natural dispersion from these refuges ensures that some beneficials will visit back yards but they will not stay unless food, host and shelter resources are available. Native plants have closer affinities with native insects and therefore provide most of these resources. A garden with a good diversity of local native flora in and around back yards, will improve the abundance and diversity of local, beneficial arthropods. Native flora also provides natural overwintering sites for many beneficial insects and it is useful to leave at least a small area of native vegetation undisturbed during fall and winter.
  • Some kinds of beneficial insects (e.g. lady beetles, lacewings, predatory mites) are available for purchase from commercial suppliers. However, benefits from introducing these beneficials are usually limited and short-lived. Upon release, commercially obtained lady beetles and lacewings often disperse and may rapidly leave your backyard despite the presence of prey and suitable nectar resources. Generally, it is more effective and sustainable to create a garden habitat that will be colonized by beneficials naturally.
     

Images

+ Show larger images

 
Caption: Adult hover fly (Sphaerophoria sp.) (Syrphidae)
Photo by: D.G. James
Caption: Larva of hover fly (Syrphidae)
Photo by: D.G. James
Caption: Larvae of hover flies (Syrphidae) feeding on aphids
Photo by: D.G. James