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Ministry of Agriculture, Food and Rural Affairs

Assassin bugs

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Beginner

Scientific Names 
There are several different species of assassin bugs including Acholla multispinosa (DeGeer), Zelus luridus Stal. The most abundant assassin bug in Ontario apple orchards is Acholla multispinosa (DeGeer).

Identification
A. multispinosa is described below:
Eggs:

  • In masses containing about 24 eggs on buds or twigs and limbs.

Nymphs:

  • Five nymphal instars,
  • Early instars appear black,
  • Later stages are light coloured and possess wing pads (immature and undeveloped wings).

Adults:

  • 1-2 cm in size,
  • Dark brown to grayish brown in colour,
  • Raptorial front legs,
  • Large beaks used for feeding on prey, held under the body in a visible longitudinal groove when not in use,
  • Elongated head,
  • Abdomen is widened in the middle, not completely covered by the wings,
  • Lifestage most commonly see in orchards.

Often Confused With

  • Leaf footed bugs - Leaf footed bugs lack a longitudinal groove in which the beak fits. The hind legs are enlarged and flattened, giving the appearance of a leaf. 

Interaction With Host
Both nymphs and adults are predaceous and feed on all life stages of green apple aphid, adult leafhoppers and some caterpillar larvae. Nymphs appear in early June and adults in late July to early August.

Period of Activity
Petal fall through early August.

Insects Attacked
Larvae and adults are generalist predators but may also be pests of fruit.

Monitoring and Management
Adults and nymphs are found in terminals during tapping and regular orchard monitoring.

Advanced

Scientific Names 
There are several different species of assassin bugs including Acholla multispinosa (DeGeer) and Zelus luridus Stal. The most abundant assassin bug in Ontario apple orchards is A.multispinosa.

Identification
There are several different species of assassin bugs and they vary greatly in size, form and colour. A. multispinosa is described below:

Eggs: Egg masses containing about 24 eggs are laid on buds or twigs and limbs.

Nymphs: Early instar nymphs appear black, while later stages are light coloured and possess wing pads (immature and undeveloped wings). There are five nymphal instars.

Adults: Adults are large insects (1-2 cm in size), dark brown to grayish brown in colour. They have raptorial front legs and a short, curved, three-segmented proboscis or beak used for capturing, subduing and feeding on prey, that is held under the body in a visible longitudinal groove when not in use. They have an elongated head and their abdomen is widened in the middle that the wings do not completely cover. They are slow moving and are the lifestage most commonly seen in orchards.

Often Confused With

  • Leaf footed bugs - Proboscis or beak is held under the body when feeding on plant material or between legs when not in use. Leaf footed bugs lack a longitudinal groove in which the beak fits. The hind legs are enlarged and flattened, giving the appearance of a leaf. 

Interaction With Host
Both nymphs and adults are predaceous and feed on all life stages of green apple aphid, adult leafhoppers and some caterpillar larvae. Nymphs appear in early June and adults in late July to early August. Nymph development takes approximately 65-95 days depending on temperature and availability of insect prey. Adult assassin bugs live for a further 6-10 months. There is one generation each year. Assassin bugs feed on their prey by puncturing them with their proboscis, then injecting saliva to paralyze the prey, and then suck up the body fluids.

Period of Activity
Petal fall through early August.

Insects Attacked
Larvae and adults are generalist predators but may also be pests of fruit.

Monitoring and Management
Adults and nymphs are found in terminals during tapping and regular orchard monitoring.