Ladybird, ladybug, lady beetle, ladybird beetle…what’s in a name? I can answer this Shakespearian question with one word: Confusion!
Although they’re commonly called ladybugs (as well as ladybirds and ladybird beetles), the term "bug" is used for the group of insects that classified as "true bugs" (Order: Hemiptera). Common examples of the true bugs in the order Hemiptera include leaf-footed bugs, stink bugs and boxelder bugs. Because “ladybugs” are a type of beetle (Order: Coleoptera), the term lady beetle is correct technically and is actually recognized as the official common name by the Entomological Society of America.
That perplexity goes a step further with the twice-stabbed lady beetle. There are at least three species which can bear that common name: Chilocorus cacti, Chilocorus stigma and Olla v-nigrum. All three of them are beneficial insects. And, luckily for Texas gardeners, all three are among the 136 species of Coccinellidae (the scientific name for the lady beetle family) found in Texas.
The 3 species labeled “twice-stabbed” are black and shaped somewhat like another famous beetle from the Volkswagen family. Each species has one bright red spot on each wing cover. For Texas gardeners, perhaps the most valuable common traits that the 3 species share are the strong mouthparts and the resulting choice of prey. These powerful mouthparts enable them to chew through the armored covering of many scale insects.
In our area, scale insects are among the pests found on many ornamental plants. They can be particularly destructive to all citrus varieties. So, it becomes important for gardeners to become familiar with this lovely (despite the gory name) trio.
Aside from looking very much alike, these beetles have many other characteristics in common. The life cycle is a complete metamorphosis (egg, larva, pupa, adult) and is usually completed within 2-3 weeks. All larvae are predacious and highly mobile, so they start feeding immediately—on each other, if other prey is not readily available.
Adults live another 2-5 weeks. In warmer climates, there can be several generations a year. Mature adults hibernate in ground litter when it is cool enough.
Being voracious, efficient predators, these lady beetles seem to have taken a lesson from their own experience as hunters and have evolved with some interesting defenses against animals that prey on them. Their red and black coloring may be an example of aposematosis, in which the bright colors warn predators of toxicity and/or bad taste. Also, female adults can “reflex bleed” from leg joints. The blood (hemolymph) has a repulsive smell that can fend off predators such as small birds and lizards.
Differences can be just as important as likenesses in identifying this trio of natural allies. Chilocorus stigma is native to the United States and occurs throughout the country, except in California. Adults are 3.75 to 5 mm in length and favor arboreal habitats such as orchards, tree plantations, and forests.
C. stigma starts life as a very small (1.1mm) orange egg laid on its side, either singly or in small groups on stems and leaves. When it hatches, the larva resembles a miniature black or brown alligator covered with black spines.
The larva will go through four instars before it pupates. The pupa is shiny and mottled with black and brown. It does not form a cocoon. C. stigma is one of the most important predators for Florida red scale, a pest on citrus crops, since this scale is actually its preferred dinner. Females even hide their eggs under empty scale coverings.
Apparently, Chilocorus cacti is a relatively recent immigrant to Texas via New Mexico. It is especially welcomed here because it feeds predominantly on scale insects. And like the other two species it resembles, it also includes aphids, caterpillar eggs, mites, and other soft-bodied insects on its menu.
Remember the old maxim “The enemy of my enemy is my friend”? Nature has presented gardeners with three potentially powerful friends if we can avoid poisoning them along with our “enemies.”
Our friends are just as susceptible to broad-spectrum insecticides as are the pests. It may be well worth the effort to try less noxious means of control, such as good cultivation practices and selecting less susceptible varieties of plants, and giving our friends a chance to show us their value.
Beneficials in the Garden & Landscape is an Earth-KindTM program coordinated through Extension Horticulture at Texas A&M University. Earth-Kind uses research-proven techniques to provide maximum gardening and landscape enjoyment while preserving and protecting our environment.
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