Anita’s Blog – Blue-eyed Ensign
- jjvanm
- 2 days ago
- 5 min read
Updated: 1 day ago
This is about a family of insects I was surprised to see at a black light and moth sheet.
My curiosity increased with each additional species.
I’ll start with what’s interesting about these insects, so you keep reading. Humans aren’t fond of these particular insects, but they are important to a LOT of predators that depend on protein-rich diets.
The Predators:
Insects and arachnids: spiders, praying mantises, beetles, centipedes, ants and certain parasitoid wasps
Reptiles and amphibians: lizards, geckos, frogs, toads and rough green snakes – I wasn't familiar with the rough green snake until I photographed one on May 28.
Mammals: mice, rats, shrews, opossums
Predatory nematodes
Birds: insect-eating birds
Owls
Chickens
House centipedes that actively hunt indoors
Cats: mostly for sport, not for food.
Did you guess which insect this story is about? It’s the unpopular cockroach. The ick factor aside, keep reading. Of the nearly 4,500 species worldwide, only a handful are considered household pests and get all the bad publicity.
Interestingly, were it not for the trillion or so wild cockroaches that live peacefully in forests and fields, the Earth would suffer severe ecological disruptions, according to an April 16, 2024, science Web article at How Stuff Works, by Karen Kirkpatrick entitled “What if There Were No Cockroaches.”
“Wild cockroaches are vital to nature's cleanup crew. Without them, forests would accumulate rotting debris, soils would lose essential nitrogen, and many predatory animals would starve.”
Roaches consume decaying organic matter, leaf litter, and feces, trapping atmospheric nitrogen. In turn, “their feces return bioavailable nitrogen to the soil, which is vital for plant and tree growth. Without cockroaches, forest health would rapidly deteriorate.”
Something to think about: Without cockroaches, decomposing material would pile up in the wild, stifling ecosystems.
Of the more than 4,500 species of cockroaches worldwide, roughly only 30 species are nuisance species (again, worldwide); approximately 55 to 70 species in the United States and North America, and only about four to six species that are common indoor pests. Texas has more than 30 species of cockroaches; South Texas has about a dozen naturally occurring, wild, and indigenous cockroach species living outdoors; very few species are indoor pests.
The Rio Grande Valley's hot, humid climate provides an ideal habitat for a variety of cockroach species.
Common species we might encounter indoors include:
German Cockroach, Blattella germanica: Small, light brown with two dark stripes behind its head. They are the most common home-invading pest in the Valley.
American Cockroach, Periplaneta american): The largest common house-invading roach in the U.S. (up to 2 inches long), reddish-brown, and sometimes called a "palmetto bug" or "waterbug.”
Brown-Banded Cockroach, Supella longipalpa: Problematic indoor pests; warm, dry conditions, cluttered environments like cardboard, paper piles, they like starch and glue, (book bindings); prolific breeders; can carry disease-causing bacteria.
Oriental Cockroach, Blatta orientalis: Often referred to as "water bugs," these are dark brown or black and prefer damp, cool environments like basements, sewers, and drains.
The more common species we might encounter outdoors include:
Asian Cockroach, Blattella asahinai: Practically identical to the German cockroach, but they are strong fliers. They are active in the RGV at night and are highly attracted to exterior lighting.
Field Cockroach, Blattella vaga: Often found in lawns, leaf litter, and compost.
Smokybrown Cockroach, Periplaneta fuliginosa: Dark mahogany or black, strong fliers that live mostly in outdoor, humid environments like mulch and woodpiles.
Following is an alphabetical list of cockroach species I have encountered at the black light and moth sheet set up as identified by iNaturalist.org:
American Cockroach, Periplaneta americana
Asian Cockroach, Blattella asahinai
Australian Cockroach, Validiblatta australasiae
Boll’s Sandroach, Arenivaga bolliana
Field Cockroach, Blattella vaga
Genus Blattella, a cosmopolitan wild cockroach (possibly Field Cockroach)
Pale-bordered Field Cockroach, Pseudomops septentrionalis
Surinam Cockroach, Pycnoscelus surinamensis
Cockroaches are not some of the most attractive insects, so smaller photos should suffice:
Top row, American, Asian, Australian Cockroaches
2nd row, Boll's Sandroach, Field Cockroach, and Genus Blattella cockroach
3rd row, Pale-bordered Field and Surinam Cockroaches
The Good News.
Don’t swat this little flyer. It’s a special wasp, generally found indoors – you’ll see why.
The Blue-eyed Ensign Wasp, Evania appedigaster, is a Common Cockroach Egg Parasitoid Wasp, a beneficial, harmless insect known for its bright electric-blue eyes. It is named because the wasp carries its tiny, triangular shaped abdomen high on its body attached by a thin stalk. As it walks, it bobs its abdomen up and down, making it resemble a small, waving signal flag, according to Wikipedia.
The adult wasps are our friends, they are harmless to humans. The wasps target the egg cases (oothecae) of several species of domestic cockroaches to lay its eggs. A female wasp lays a single egg inside the cockroach's egg case, and the developing larva feeds entirely on the roach eggs inside, acting as a natural pest control.
The primary cockroach hosts around our area used by this wasp include:
American cockroach (Periplaneta americana)
Australian cockroach (Periplaneta australasiae)
Brown cockroach (Periplaneta brunnea)
Oriental cockroach (Blatta orientalis)
Just so you know: An ensign is a flag. Nautically, ensign is an official national flag flown at the stern of a vessel when in port or anchored, denoting the country of the naval or merchant vessel. The U.S. Navy uses the standard Stars and Stripes as its ensign. Ensign also is the rank of the most junior commissioned officer in the U.S. Navy; its use as a rank is from the time when the junior officer in infantry regiments carried the unit’s identifying flag, or “ensign.”
What you can do – or rather not do. Don’t trim the palm frond skirts.
The more roaches in palm tree skirts, the more that are not in your home, is my theory. Palm trees attract cockroaches for shelter, moisture, and food. Dead, brown fronds that are not trimmed off create a thick, dark, and humid canopy where roaches love to nest. Cockroaches are scavengers – opportunistic omnivores. They feed on rotting fruit and seeds dropped by trees and other rotting vegetation, dead insects, small animal carcasses, feathers, fungi, mold and other animal droppings – basically anything derived from something that was once alive.
Fun facts for those who like numbers: (From an AI profile run by Quora, author NovaPrism.)
“It is estimated that there are trillions of individual cockroaches in the world, with defensible scientific estimates placing the global population roughly between 100 billion and one quadrillion.
“The scientific and historical context of their massive populations:
Species Diversity: There are over 4,500 cataloged species of cockroaches, but less than one percent of these are considered pests that enter homes and businesses.
The "Trillions" Estimate: Because these insects live deep in forests, caves, and environments untouched by humans, exact counting is impossible. Entomologists use insect-abundance literature and habitat scaling to arrive at the 10 trillion central estimate.
Global Distribution: Cockroaches thrive on every continent except Antarctica and are heavily concentrated in tropical and subtropical climates, as well as urbanized human settlements. “
Further Reading
Texas A&M AgriLife Extension “Cockroaches in the Texas Landscape”
AgriLife Extension Texas A&M System pdf prepared by Wizzie Brown, Michael Merchant, and Roger E. Gold.
Google: Wikipedia’s List of cockroaches in Texas
