Hippodamia convergens is shaped like a dome and is yellow/red or brownish-red with 12 black spots on its elytra, which cover the wings. It is not as round as most lady beetles. Its legs and underside of its body are all black. The prothorax, which is the section between the head and the elytra on the back, is black with a white border and two white lines in the middle. These two white lines angle in towards each other; the lines are converging, which is where the common name of this species comes from.
Eggs are typically 1 to 1.5 mm, long, narrow, and pointed at one end. Larvae look like tiny alligators and have orange spots on their backs. Pupae are orange with black spots and are dome-shaped. (Casey, 1899; Jaques, 1951; "Lady Beetles", 2012)
Hippodamia convergens can be found in most of the Nearctic and Neotropical regions. It is a common species throughout the United States, ranging from New Jersey to Texas to California. It also common in Canada and South America. (Casey, 1899; Jaques, 1951; The Michigan Entomological Society, 2005)
Hippodamia convergens, the convergent lady beetle, lives in many habitats including forests, grasslands, farm lands, and suburban gardens. Convergent lady beetles are found on crops in gardens and farms where there are plenty of aphids and other prey to eat. Crops that they usually live on are wheat, sorghum, and alfalfa. During the winter, H. convergens can be found in hiding under logs, ground-covering vegetation, and even in buildings. (The Michigan Entomological Society, 2005)
Hippodamia convergens goes through complete metamorphosis, with life stages of egg, larva, pupa, and adult. Eggs hatch after about a week, and then larvae have four stages called instars. Larvae develop through these instars over two to three weeks. Convergent lady beetles can change their development when food levels are low, a behavior that is unique to this species. These lady beetle larvae wait until they weigh between 5 to 35 mg before they pupate. To pupate, the final larval instar often attaches itself to a leaf right before it molts and forms a pupa. H. convergens usually has two generations a year, with eggs being laid in spring, and another group of eggs laid in the fall. When food is not available, or when temperatures are very high or very low, H. convergens can enter diapause. Diapause is similar to hibernation, where development of the beetle stops, and the beetle waits out the harsh conditions. The first generation of the year of H. convergens usually will enter diapause during the summer when temperatures get high, while the second generation enters diapause for the winter. (Phoofolo, et al., 2009; Shelton, 2009; Vargas, et al., 2012; "Lady Beetles", 2012)
Hippodamia convergens has two generations a year. One group of eggs are laid in the spring, while another generation of eggs are laid in the fall. Females can enter reproductive diapause during periods of extreme temperatures and when not enough food is available. This allows the female to wait out the harsh conditions and instead lay eggs at times when the environment allows for easier survival for offspring. Females also will time their egg laying so that larvae will hatch when aphid populations are largest. This means that larvae will have the most food possible, and will be more likely to survive. A female can produce 200 to 500 eggs during her lifetime. (Hodek and Cerngier, 2000; Michaud and Qureshi, 2006; Sluss, 1968; Vargas, et al., 2012)
There is no information about parental investmen in this species, but like most lady beetles, H. convergens probably provides nutrients in eggs for the offspring to grow and develop. Otherwise, it probably does not provide any parental care.
It takes about 4 to 7 weeks for H. convergens to develop from egg to an adult. Adults live for a few weeks to months after that, with the second generation going into hiding for the winter and emerging again in the spring. (Shelton, 2009; "Lady Beetles", 2012)
Hippodamia convergens usually lives alone, except during the winter. While hiding out for the winter, hundreds of H. convergens may gather in groups. This species is mostly active during the day. Adults will fly from plant to plant to find prey, while larvae move from plant to plant by crawling from leaf to leaf. Larvae usually follow the veins on the leaves. (Purandare and Tenhumberg, 2012; Sluss, 1968; The Michigan Entomological Society, 2005)
To find prey, H. convergens uses sight, smell, and detects chemicals. Other species of lady beetles can find aphids by detecting pheromones and chemicals produced by the aphids. Aphids also produce a substance called honeydew, which H. convergens and other lady beetles can use to find the aphids. Honeydew may also increase egg laying in H. convergens, meaning that females will lay eggs when aphids are near so that the larvae that hatch will have prey to eat. Larvae also can use chemicals produced by aphids to find them, though larvae probably are more random in searching for prey than adults. Larvae use mostly touch to find prey, and will crawl along leaf veins until they either detect an aphid chemical or just bump right into an aphid. (Darby, et al., 2003; Jamal and Brown, 2001)
Hippodamia convergens is a predator. It feeds on other insects and sometimes on small arthropods. Convergent lady beetles typically eat aphids, scale insects, and plant mites. Cotton, pea, melon, cabbage, potato, green peach, and corn leaf aphids are all types of aphids that convergent lady beetles have been seen eating. Hippodamia convergens also eat the eggs and larvae of other insects, such as stinkbugs, asparagus beetles, and potato psyllids. Although larvae and adults both mostly eat aphids, adults will eat pollen in the fall just before hibernation. This causes the beetle to gain extra fat that it will use while hibernating for winter. When other food sources are not available, H. convergens will become cannibalistic and eat its own eggs and larvae. (Saito and Bjornson, 2006; Shelton, 2009; The Michigan Entomological Society, 2005)
Hippodamia convergens has a large appetite and may eat between 40 to 75 aphids per day. These lady beetles eat the most aphids when temperatures are around 23 degrees Celsius. This shows that these beetles are better at controlling the size of aphid populations at this warm temperature. (Katsarou, et al., 2005; Shelton, 2009)
Insect predators that prey on many different insect species, such as Geocoris bullatus and Nabis alternatus, are known to eat the eggs of H. convergens. Birds are often predators of H. convergens as well. To defend against predators, H. convergens and most lady beetles can release toxic chemicals from the joints in their legs, called reflex bleeding. They also have something called aposematic coloration. Predators know that brightly colored insects are often poisonous and tend to not eat them. The red and black coloration of H. convergens acts as a warning signal to predators that it is a poisonous insect, and predators are less likely to attack as a result. (Dolenska, et al., 2009; Takizawa and Snyder, 2012)
Hippodamia convergens is a significant predator of many crop pests, particularly aphids. They also eat many other insects. Birds and predator insects such as Geocoris bullatus and Nabis alternatus feed on H. convergens. Disease-causing organisms such as Microsporidia use the bodies of convergent lady beetles as hosts, which causes delayed development in larvae. These organisms can be transmitted from beetle to beetle of this species because H. convergens often eats its own eggs and larvae. The braconid wasp Perilitus coccinellae is known to use H. convergens as a host. Parasitoid wasps, which lay eggs in other insects and cause death when they emerge from the host insect, such as Dinocampus coccinellae, use convergent lady beetles as hosts. Females of this species are infected more than males with Dinocampus coccinellae. Parasites travel with their host lady beetles that are sent all over the world for farmers to use to control aphid populations. This has caused an increase in these parasites in the areas of the world where they are sent. (Bjornson, 2008; Saito and Bjornson, 2006; Sluss, 1968)
Since Hippodamia convergens is used to reduce the size of crop damaging aphid populations in many places around the world, it can bring parasites and disease-causing microorganisms with it. The transportation of these lady beetles has increased the risk of bringing parasites and disease-causing organisms into the United States, as well as to other places, which could cause problems for humans. (Saito and Bjornson, 2006)
Hippodamia convergens provides great economic benefit to humans. Convergent lady beetles are raised by humans and sold as pest control for farms and gardens, because they eat so many aphids and other crop pests. By eating so many crop pests, H. convergens can reduce the population of these insects, and prevent crop damage, which keeps farmers from losing too much money. (Bjornson, 2008; Casey, 1899; Michaud and Qureshi, 2006; Saito and Bjornson, 2006; Shelton, 2009)
No additional comments.
Adriana Saroki (author), University of Michigan Biological Station, Angela Miner (editor), Animal Diversity Web Staff, Brian Scholtens (editor), University of Michigan Biological Station.
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