No assassinations today! But an "assassination attempt."
There it was, a leafhopper assassin bug, Zelus renardii, waiting for prey atop a Mexican sunflower, Tithonia rotundifola in a Vacaville pollinator garden. Yes, it's native to North America.
The assassin bugs, family Reduviidae, are ambush predators. When they ambush a predator, they stab it with their rostrum, inject venom, and suck out the juices. Or as UC Berkeley entomologists Jerry Powell and Charles Hogue write in their book, California Insects, "The victims, which include all kinds of insects, are snatched by quick movements of the forelegs, and immediately subdued by a powerful venom injected through the beak."
UC Statewide Integrated Pest Management Program (UC IPM) says that "Assassin bug adults and nymphs (immatures) have an elongate head and body and long legs. The narrow head has rounded, beady eyes and long, hinged, needlelike mouthparts. Adults and nymphs can walk rapidly when disturbed or capturing prey. Adults tend not to fly."
"Assassin bugs can occur on almost any terrestrial plant including row and tree crops and gardens and landscapes. All species are predators of invertebrates or true parasites of vertebrates," UC IPM relates. "Most assassin bugs feed on insects including caterpillars, larvae of leaf beetles and sawflies, and adults and nymphs of other true bugs. Nymphs and adults ambush or stalk prey, impale them with their tubular mouthparts, inject venom, and suck the body contents. Zelus renardii produces a sticky material that helps it adhere to plant surfaces and ensnare prey."
Some 7000 species of assassin bugs reside throughout the world. When they feed on such agricultural pests as fleahoppers, lygus bugs, aphids, caterpillar eggs and larvae, they are considered biological control agents.
However, "assassin bugs are not considered to be important in the biological control of pests, unlike predatory groups such as bigeyed bugs and minute pirate bugs," UC IPM says. "Assassin bugs are general predators and also feed on bees, lacewings, lady beetles, and other beneficial species. Certain species feed on the blood of birds, mammals, or reptiles, including conenose bugs and kissing bugs (Reduviidae: Triatominae)."
The one we saw today?
A long-horned bee, Melissodes agilis, stopped for a sip of nectar, spotted the assassin bug, and buzzed off, leaving only its shadow behind.
Folks will do just about anything to remove cockroaches from their homes, but when it comes to UC Davis Picnic Day, you can't remove people from them.
Nor would UC Davis Department of Entomology and Nematology want that. Roach Races are an integral part of Picnic Day.
Hundreds of cheering fans showed up at Briggs Hall for the department's Roach Races, held Saturday, April 23 during the 108th annual UC Davis Picnic Day.
Entomology students organized and directed the races, but the real heroes and heroines were the American roaches, reared by UC Davis entomologists and ready to run.
Spectators applauded them wildly, but gasped when a few of the two-inch insects tried to escape into the crowd.
Cockroaches, which belong to the order Blattodea, are primarily nocturnal and “have a tendency to scatter when disturbed,” according to the UC Statewide Integated Pest Management Program (UC IPM).
That they did during the Roach Races.
“There are five species of cockroaches in California that are commonly regarded as pests: German cockroach, brownbanded cockroach, oriental cockroach, American cockroach, and Turkestan cockroach," according to UC IPM. "Indoor cockroaches are known as significant pests of public health, and outdoor species that find their way inside are considered serious nuisance pests as well as potential public health pests. Most cockroaches harbor within moist, dark crevices when not foraging for food. They crawl quickly and may climb rough surfaces. A few species can fly short distances or glide as adults during warm nights, but most have no wings, reduced wings, or otherwise do not fly."
UC IPM says that "Indoor infestations of cockroaches are also important sources of allergens and have been identified as risk factors for development of asthma in children, especially within multi-unit housing environments. The levels of allergens present have been directly correlated to both cockroach density and the conditions that contribute to heavy infestations, such as housing disrepair and poor sanitary conditions.”
Sometimes youngsters participating in Maggot Art, another insect-activity hosted by the UC Davis Department of Entomology and Nematology during Picnic Day, get so attached to the maggots creating art for them that they ask to take them home.
Not so with the UC Davis Roach Races. Not a single person--not a single one--asked to take one home.
Call them ladybugs, call them ladybirds, call them lady beetles, call them Coccinellidae, or just call them aphid eaters or deluxe aphid eaters.
And while you're at Briggs Hall, check out the insect-related displays and activities planned and coordinated by entomology doctoral candidate Danielle Rutkowski of the UC Davis Graduate Student Association. The events range from Roach Races (cheer on your favorite roach) to Maggot Art (dip a maggot in non-toxic, water-based paint and create a masterpiece worthy of framing--or at least, it can join your refrigerator art).
They're curious little critters.
When solider beetles (family Cantharidae) go on patrol in your garden, don't kill them. They're not being deployed to harm you.
They're the good guys. They eat aphids and other soft-bodied insects.
Sometimes called "leatherwings"--they look like the insect equivalent to the British soldiers in the American Revolution soldiers--soldier beetles compete with lady beetles (aka ladybugs), lacewings, damsel bugs, long-legged flies and other insects for aphids. Larvae of lady beetles and syrphid flies (aka flower flies and hover flies) also feast on aphids.
The UC Statewide Integrated Pest Management Program (UC IPM) provides a good description of the soldier beetle:
"Adult soldier beetles are elongate and usually dark brown to black with orange, red, or yellow. The head is commonly bent downward. The antennae are 11-segmented, threadlike, and commonly held forward of the body. The pronotum is usually wider than the head and wider than long. The wing covers are smooth to velvety appearing and soft and flexible, giving rise to the common name leatherwings. Adults range from 1/16 to 1-1/8 inches (1.5 to 28 mm) long, varying by species....About 160 species of soldier beetles in 11 genera occur in California. Common genera include Cantharis, Chauliognathus, and Podabrus."
Adults are active during the day and usually observed on flowers or leaves infested with aphids or other honeydew-excreting insects," UC IPM says. "When disturbed, adults may withdraw their legs and drop to the ground as if dead. Adults' blackish and red coloration alerts vertebrate predators that cantharid beetles are distasteful; adults, larvae, and pupae can excrete noxious, defensive chemicals from specialized abdominal glands."
None that visited our garden last weekend dropped to the ground. We didn't disturb them, either (we were using a 200mm macro lens).
And curious photographers.
Last weekend we spotted cottony cushion scale, Icerya purchasi, infesting the twigs and branches of our Nandina (Nandina domestica), planted 22 years ago. This scale insect is more commonly found on citrus crops and Pittosporum, but there it was.
It's a native of Australia and apparently made its way to California on acacia plants around 1868 or 1869, and began infesting citrus groves in southern California. It's now found throughout the world, wherever citrus is grown. Pick it up and it's as light as a feather and soft as cotton.
If you look closely at a mature cottony cushion scale (hermaphrodite), you can see that it's reddish brown with black hairs. It produces a ridged white egg sac encasing hundreds of brilliant red eggs--the color of pomegranate kernels.
"Like other scales, cottony cushion scale decreases the vitality of its host by sucking phloem sap from the leaves, twigs, branches, and trunk," according to UC IPM. "Feeding can result in defoliation and dieback of twigs and small branches when infestations are extremely heavy. Heavy populations can severely reduce the yield of citrus trees. Like soft scales, cottony cushion scale excretes honeydew, which is usually accompanied by blackish sooty mold growth and ants."
"Cottony cushion scale has two to three generations a year," UC IPM tells us. "Unlike most other scales, it retains its legs and its mobility throughout its life. Cottony cushion scale completes its life cycle in three months during warm weather conditions."
Its most famous natural enemy is the vedalia beetle, Rodolia cardinalis, introduced from Australia in the 1890s to save California's citrus crops. Vedalia beetle vs. cottony cushion scale--this is a clear-cut case of successful biological control. Vedalia beetles are distinguished by their darker red domes with splotchy black markings.
Another natural enemy is the parasitic fly Cryptochaetum iceryae, which lays its eggs inside the cottony cushion scale. "It deposits one to four eggs inside each second-instar, third-instar, or adult female scale body," UC IPM points out. "The eggs hatch into larvae that feed within the scale." (See more information on the UC IPM website)
Interesting that we've never found the cottony cushion scale on our nearby tangerine and lemon trees. "Marked Safe from Cottony Cushion Scale."