The Leafhopper Assassin Bug (Zelus sp.)
Leafhopper assassin bugs are about 1/2 inch long and red, brown to yellowish-green. Females deposit egg masses that are barrel-shaped and dark brown with a white cap. Egg masses are laid openly in groups on plant surfaces. Immature nymphs resemble adults but are wingless and develop through five molts (instars) into adults in about two months (depending on weather conditions).
Adults are poor fliers, and both adults and nymphs move rapidly when disturbed. The front legs have no spines but are covered with a sticky substance with which they catch their prey. Leafhopper assassin bugs prey on a broad range of insect pests including fleahoppers, lygus bugs, aphids, caterpillar eggs, caterpillar larvae and boll weevils. They will also prey on other predaceous insects such as lady beetles and big-eyed bugs—as is typical for many insect predators that are generalist feeders. However, their net impact makes them effective predators.
General Overview of Assassin Bugs
Assassin bugs are widely distributed throughout the Galveston-Houston region. Assassin bugs are usually dark-colored, with combinations of gray, green and black and are members of a large family of bugs (known as Reduviidae). Assassin bugs are excellent predators and are general feeders; i.e., they prey on a diverse variety of insect pests in the garden and landscape including flies, mosquitoes, beetles and large caterpillars.
The aptly named assassin bugs often wait in hiding and ambush their prey. Typically, the eyes are large and set at the middle or rear of the head with a neck-like area behind the head. The antennae have four segments. Assassin bugs, like all true bugs, have piercing, sucking mouthparts (collectively called a beak) that are used to extract body fluids from their prey. The beak has three segments and rests within a groove between the front legs when it is not in use.
Once prey is captured and punctured, salivary secretions are pumped through a canal inside the piercing/sucking mouthpart. The salivary secretions not only serve to quickly immobilize prey but they also dissolve the prey’s internal tissues. This process enables the assassin bug to withdraw the bodily contents of its prey.
Like all members of the order Hemiptera, assassin bugs and ambush bugs go through a simple metamorphosis with egg, nymph and adult stages. In warm months, females lay eggs which are stuck in clusters to leaves and stems. After hatching, the wingless nymphs grow and molt 4 times (some species molt have up to 7 times) before becoming full-sized, winged adults. Adults are usually the overwintering stage.
In general, assassin bugs hunt on various types of vegetation, including trees, weeds and bushes. Assassin bugs are able to fly but they are poor fliers in general with some notable exceptions.
Although most assassin bugs are slow-moving and nonaggressive, they will use their rostrum in self-defense if handled carelessly. Such bites may be rather painful to humans because the bugs inject the same salivary secretion used to dissolve the tissues of their prey. This results in the death of a small area of cells at the site of the bite. The symptoms are an intense burning sensation, often followed by a small, itchy lump that may persist for several days. However, no true toxin is involved so it is rare for the reaction to last long or to extend beyond the site of the bite. Some bites occur when the bugs are purposely handled out of curiosity, but most happen through accidental contact while gardening or working in the open. The sharp pain associated with assassin bug bites is usually enhanced by the surprise accompanying the experience.
The beneficial qualities of assassin bugs far outweigh their negative potential, and learning to get along with these indispensable predators is in our own best interest.
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