Milkweed Assassin Bug – A Common Beneficial Predator in the Garden
By George Giltner, Master Gardener
Zelus longipes is the ‘milkweed assassin bug’ or the ‘longlegged assassin bug’, but it is commonly misidentified as the nymph of leaffooted bugs or as another sap sucking plant pest in our area. But take a minute to ID this great predator that feeds on a wide range of soft-bodied prey in flower and vegetable gardens. Just by observation you may notice a fly, mosquito, cucumber beetle, armyworm, rootworm or other caterpillars captured in the long spearing beak. Also look for the long legs which are hairy within range of a magnifying glass. The color is usually yellow to orange to a reddish orange on the stomach side with black wings present on the adults. An orange triangle may be present in front of the wings. This species has great variation in size and color. However the adults and nymphs have a characteristic pear-shaped head, constricted neck, black eyes, and a forward moving beak that help in identification as a predator.
The economic importance of the milkweed assassin bug is as a major predator of crop damaging pests like the fall armyworm, Asian citrus psyllid, cornsilk flies (causing larvae damage of corn), and the genista broom moth (caterpillar attacks Texas laurel, crape myrtle, honeysuckle, and Laburnum.
Their preying behavior is fun to watch, especially around flowers. They hide in the leaf foliage with their frontal legs raised for an attack. As the ends of these legs contain a sticky substance, they pounce on prey and immediately insert the forward moving beak into the prey. The prey is paralyzed with an injection of liquid saliva, then it is digested and ingested. The prey may be up to seven times the size of the milkweed assassin bug.
Many adults and nymphs have been noticed overwintering around vegetation and flowers in Beauregard Parish. The constricted neck of the milkweed assassin bugs readily separates their wrongful ID as leaffooted bugs (nymphs or adults).
Gardeners should learn to identify beneficial insects like the milkweed assassin bug. These beneficials keep an ecological balance in check between predators and prey. When all insects on plants are sprayed with wide range insecticides early in spring, it is usually the pests that have the reproductive advantage to cause outbeaks and major pest problems.