Bed Bug Biology
Introduction to the Bed bug Lifecycle
The bed bugs that are infesting homes today are the descendents of cave dwelling bugs that originally fed on the blood of bats. When humans began living in the caves, the bugs began feeding on humans. Later, when humans moved out of the caves and started their agricultural civilizations, the bugs moved with them.
Since that time, humans have carried bed bugs all over the world.
Bed bugs belong to a family of insects called Cimicidae. All members of this family feed exclusively on blood. The common bed bug (Cimex lectularius) has five developmental life stages. Each immature life stage (called nymphs or instars) must take a blood meal in order to develop into the next life stage. Because bed bugs, like all insects, have their skeleton on the outside of their body (exoskeleton)they have to shed their exoskeleton in order to grow larger. This shedding of the exoskeleton is called molting. Adult bed bugs have a life span of nearly one year depending on regular access to blood meals and favorable temperatures.
Bed bugs have a cryptic lifestyle, meaning they spend the majority of their time hiding together in cracks and crevices where they will not be seen or disturbed. However, they become active at night, between and . It is during this time, when the human host is typically in their deepest sleep, that bed bugs like to feed.
Bed bugs are known to travel many meters to reach their human host. Bed bugs are attracted to CO2 produced by the host exhalations, and they are also attracted to body heat. However, bed bugs are able to move very quickly, and it is thought that they do a lot of wandering around before they are able to locate their food. Ideally, most bed bugs would like to aggregate near the host’s bed, on the mattress or in the box springs, when they are not feeding. However, this is not always possible in heavy infestations where bed bugs are crowded and many bed bugs have to seek refuge at distances several meters from the host.
Once a bed bug finds the host, they probe the skin with their mouth parts to find a capillary space that allows the blood to flow rapidly into their bodies. A bed bug may probe the skin several times before it starts to feed. This probing will result in the host receiving several bites from the same bug. Once the bed bug settles on a location, it will feed for 5-10 minutes. After the bed bug is full, it will leave the host and return to a crack or crevice, typically where other bed bugs are aggregating. The bed bug will then begin digesting and excreting their meal. Bed bugs usually feed every 3-5 days, which means that the majority of the population is in the digesting state, and not feeding most of the time.
After feeding, adult bed bugs, particularly the males, are very interested in mating. Cimicid bugs have unique method of mating called traumatic insemination. This mating behavior is considered traumatic because the male, instead of inserting his reproductive organ (paramere) into the female genitalia, he literally stabs it through her body wall into a specialized organ on her right side.
The number of egg batches a female will produce in her lifetime is dependent on her access to regular blood meals.
• A female bed bug will produce between 1- 7 eggs per day for about 10 days after a single blood meal.
• She will then have to feed again to produce more eggs.
• A female can produce between 5 and 20 eggs from a single blood meal.
• The number of male and female eggs produced is about the same (1:1 ratio).
• A single female can produce about 1100 eggs in her whole life.
• Eggs can be laid singly or in groups. A wandering female can lay an egg anywhere in a room.
• Under optimal conditions, egg mortality is low and approximately 97% of the bed bug eggs hatch successfully.
• At room temperature (>21° C), 60 percent of the eggs will hatch when they are 6 days old; >90 percent will have hatched by the time they are 9 days old. • Egg hatch time can be increased by several days by lowering ambient temperature (to 10° C). • Due to the large numbers of eggs a female can produce under optimal conditions (temperatures >21° C but < 32° C, and in the presence of a host), a bed bug population can double every 16 days.
Nymph Development Time
The time it takes any particular bed bug nymph to develop depends on the ambient temperature and the presence of a host. Under favorable conditions, such as a typical indoor room temperature (>21° C), most nymphs will develop to the next instar within 5 days of taking a blood meal.
Adult Bed Bug Life Span
The most recent studies indicate that a well-fed adult bed bug held at room temperature (>21°C), will live between 99 and 300 days in the laboratory. Unfortunately, we do not know exactly how long a bed bug might live in someone’s home or apartment. No doubt it will be at least several months. However, conditions are usually more challenging for the bed bugs living in human dwellings than they are in the laboratory (finding food, fluctuations in temperature and humidity, the presence of insecticides, avoiding being crushed, etc.) and these conditions will have a negative impact on bed bug survival.
Dini M. Miller, Ph.D., Department of Entomology, Virginia Tech.
Andrea Polanco, Department of Entomology, Virginia Tech.