This week a trio of perplexing unknowns arrived in the Bug of the Week mailbox. The first was an interesting brown structure about an inch long resembling Styrofoam stuck to a twig. This nifty piece of artwork, known as an ootheca, was collected by a student and submitted with an insect collection in November. After incubating in the warmth of a laboratory for several months, a blessed event occurred as dozens of tiny praying mantids hatched from eggs imbedded in the brown egg-mass. We visited other species of mantids in previous episodes of Bug of the Week.
A bevy of wax scales encrust this stem and await warm temperatures when egg production begins.
Under natural conditions, that is to say if the ootheca had remained outside, the tiny predators would have hatched in spring when prey such as small flies, caterpillars, and crickets abound. However, the warmth of the laboratory facilitated the development of the embryos and produced a batch of preemies. No worries, the tiny Carolina mantids are dining on fruit flies and awaiting their release once spring arrives. Unlike the Chinese praying mantid or European praying mantid, the Carolina mantid is a native to North America. It ranges from New Jersey, south to Florida and west to Arizona in the United States. Like other mantid species, Carolina mantids eat a wide variety of insects and spiders found in gardens and landscapes, including beneficial ones such as bees. Although egg cases of praying mantids can be purchased commercially and placed in the garden, the effectiveness of mantids as biological control agents is ambiguous at best. Nonetheless, mantids are fascinating to observe and study and several ootheca await the arrival of spring in my landscape.
The immature stage of the wax scale is called a cameo for obvious reasons.
The second unknown of the week came from a delightful Master Gardener in St. Mary’s county in Maryland. This keen observer discovered several disconcerting whitish globs on the stems of her shrubbery and correctly deduced that these were some kind of scale insect. We visited scale insects on tuliptree in “There's a sucker born every day”. The particular species of scale she discovered is called a wax scale, of which several species occur in North America, primarily in southern states. My entomological colleagues have also noted the penetration of many southern species of scales further north in recent years. In the bug world there is growing concern that climate change may be facilitating an invasion by southern pests into northern states as winter temperatures rise. Time will tell if these discoveries are temporary anomalies or the harbingers of a real trend.
Curious oblong discs lining the stem of this rose are the eggs of a katydid, but are sometimes mistaken as scale insects.
Wax scales are curious creatures with a relatively sedentary life style. Just beneath the white waxy cover of the scale is a female insect that is pinkish-red in color. After a winter of relative inactivity, the female scale produces pinkish eggs that hatch in April and May.
The small scale hatchlings are called crawlers and their mission is to disperse along branches and find suitable locations to settle on the bark. After staking their claim, crawlers insert straw-like, sucking mouthparts into the branch and suck the nutritious sap. Once settled, young scales produce wax from glands surrounding their body. At this stage, the scale is aptly called a cameo. The scale will continue to grow throughout the summer and fall, adding wax, sucking sap, and producing a sticky secretion known as honeydew. One generation of wax scales appears in Maryland each year, but in the deep South two or more generations can occur each year. Wax scales use more than 50 species of plants as food including hollies, boxwood, pyracantha, camellia, spirea, quince, and barberry.
The third “Who are you?” was also submitted from an avid Master Gardener from St. Mary’s, Maryland who photographed several gray oblong objects lining the stem of her rose bush. At first glance, these immobile discs resembled a dull version of some scale insect. However, these are really the eggs of a katydid. In temperate climates such as the one here in Maryland, resident insects have a developmental stage to withstand the months of chilly temperatures and scarcity of food. Katydids spend the winter as eggs deposited in autumn by last year’s females on twigs, branches, and other objects. When warmer temperatures return, the eggs will hatch and by summer we will once again hear the serenade of the katydids. To learn more about katydids, please visit the episode of Bug of the Week called “Katydid?”.
References
We thank Diana and the other great Master Gardeners from St. Mary’s County, Maryland for providing the inspiration for this Bug of the Week. The outstanding reference, “Insects that Feed on Trees and Shrubs” by Warren Johnson and Howard Lyon was used a reference for this Bug of the Week. For more information on Carolina mantids, please visit the following web sites:
http://animaldiversity.ummz.umich.edu/site/accounts/information/Stagmomantis_carolina.html
http://www.ca.uky.edu/entomology/entfacts/ef418.asp