Even as a trained entomologist, identifying insects is challenging.
The thing with insects is there are a lot of them – over 900,000 discovered and described species, and scientists estimate that over 10 million exist worldwide. At least once a month, an image of a specimen requires more investigation, a review of primary research, and sometimes the help of other entomologists.
Another reason identifying insects may be difficult is due to the various life stages (egg, larva, nymph, pupa, adult) and furthermore the differences in the specific larval or nymphal instar. Not only is it far more challenging to identify a butterfly as a larva compared to an adult, but very young caterpillars may have varying color patterns compared to a more mature caterpillar. For insects that undergo incomplete or gradual metamorphosis, many young nymphs resemble other species.
This article focuses on eggs found in the urban landscape during late fall and winter.
Praying Mantis Oothecae
There are two common species of praying mantises we see in Nebraska, the native, Carolina mantis, Stagmomantis carolina, and the non-native, Chinese mantis, Tenodera sinensis. Both are generalist predators and natural enemies in the garden and their diet consists of anything they can get their raptorial forelegs on, which unfortunately includes beneficial insects and pollinators, big and small.
The Chinese mantis as an adult, can grow up to 5-inches long and can be bright green or brown. The Carolina mantis at its largest is typically less than 2.5-inches long, and can be shades of green, mottled brown, even gray to black in color. Both are adapted to blending into their environment, which can be in the landscape on flowering plants, trees, shrubs, or structures like buildings, decks, and humanmade objects.
The male and female praying mantises are distinguished by their size and shape. Males are fantastic fliers with longer wings, extending past the end of their slender abdomen. Females are much stockier and cannot fly. Their wings are shorter, and their abdomens expand to accommodate eggs. Females leave hard-walled egg cases, called oothecae (ootheca is singular) before winter, which may produce hundreds of nymphs the following spring or summer.
The Carolina praying mantis ootheca is brown in color, rectangular-shaped, and slender, firmly attached to tree branches, fences, or the outside of buildings. The Chinese mantis ootheca is round with a frothy appearance. They are glued within dense vegetation attached to the stems of plants, especially in late fall when gardeners are cleaning up beds for the season.
Wheel Bug Eggs
Wheel bugs, Arilus cristatus, are large (up to 1.5 inches), gray-colored, prehistoric-looking, assassin bugs with strong, beaklike mouthparts. As adults they have a cogwheel shape on the center of their backs and are often mistaken for a slow-moving spider because their long antennae are mistaken for an extra pair of legs. Like praying mantises, they are generalist predators and though they are known to prey on the dreaded Japanese beetle, may also feed on pollinating insects like bees, flies, and beetles.
In the fall, the female wheel bug lays a dense mass of eggs on tree bark or branches. Each egg is barrel-shaped with a dark center and together the clutch of eggs, which ranges from 42 to 182 eggs, may take the form of a hexagon. Small wheel bugs hatch in April and May the following spring as small, red, nymphs and start to feed on small invertebrates in the landscape.
Garden Spider Egg Sac
Even those who despise spiders may admit the black and yellow garden spider, Argiope aurantia, is a beauty to behold in the garden. This spider has many common names like the golden garden spider, corn spider, and zigzag spider, named for the zigzag-shaped silk structure (called stabilimentum) weaved in the center of its orb web. They are known to vibrate their webs rapidly as a defense mechanism. Spiders are not often found until the end of summer when their presence in the center of their webs is noticed.
Garden spider female may produce several egg sacs in the fall, which may be found close to the web. They may be attached to a structure or protected under vegetation. Each egg sac is a brown, spherical teardrop that ranges in size from 5/8 to 1-inch in diameter. Inside are layers of eggs protected in layers of silk. The female garden spider dies, but her spiderlings emerge from the egg sac the following spring and survivors balloon to new locations.
If you find any of these eggs out in the garden during fall sanitation and clean up, try and identify them and then look for their immatures next spring and summer. Resist the urge to collect them and take them inside for the winter, as warmer temperatures stimulate eggs to hatch before there is natural food sources are available.
People always inquire how arthropods survive the winter, and now you know how to identify a few overwintering eggs.