Digital Science

Macrophages are one of many types of white blood cells (leukocytes) present in body tissues. Macrophages are important in immune response and cell stability because they mobilize in cell tissue to attack large foreign particles such as bacteria, yeast, and dead cells.

Macrophages are derived from precursor cells called monocytes that first develop in bone marrow. Monocytes enter the blood and travel throughout the body in the circulatory system.

When needed, circulatory monocytes move into tissue, where they become macrophages. Here a lung (alveolar) macrophage is seeking foreign bacteria (Escherichia coli) with specialized cell extensions called filopodia.

Macrophages engulf and digest foreign materials in a process known as phagocytosis.


Aphid wasps are specific endoparasites of aphids. Like many other wasps, aphid wasps play an important role in controlling pest insect populations. During part of their reproductive cycle, aphid wasps capture and lay eggs within the bodies of live aphids.

When aphid wasp larvae hatch from the eggs, they parasitize the aphid hosts for food. As the aphid wasp larvae develop into adults, the aphids die slowly as they are consumed from the inside out. Eventually, the adult aphid wasps leave the dead aphids, leaving hollow aphid mummies behind.

Balsa wood (Ochroma lagopus). This cross section of balsa wood shows the large conductive elements that give balsa an outstanding strength-to-weight ratio. Balsa wood is lightweight, absorbs shock and vibration well, and can be easily cut, shaped, and glued.

During the 1920's it was the perfect material for aerodynamic experimentation and design. The word balsa means raft in Spanish, and in Ecuador it is known as Boya, meaning buoy.

Bean weevils are voracious and destructive agricultural pests. Bean weevils attack dry beans, cowpeas, and lentils. Their habitats include warehouses and wherever leguminous seeds are stored. Adult bean weevils lay white eggs on dry bean seeds.

The eggs hatch in between 3 and 9 days, and the hatched larvae bore twisting tunnels into the meat of the seeds. The larvae feed for between 12 days and 6 months and then pupate for between 8 and 25 days.

When mature, adult bean weevils escape the gutted seeds by cutting neat round holes in the seed coats with specialized snouts and efficient chewing mouthparts. Unlike many other types of weevils, bean weevils do not require moisture to live and feed within seeds.

Beg bugs are small (6 mm or less), nocturnal, blood-sucking insects. Flat and oval in shape, bed bugs hide by day in cracks in walls, under wallpaper, or in bedspring frames. By night, bed bugs hunt and bite their victims for food, taking small amounts of blood and, if left undisturbed, moving short distances and biting again.

A pattern of small blood clots in a concentrated area of the skin is a sure sign of bed bug infestation. While bed bugs can live in a sort of stasis for a year or more when deprived of food, a single, well-nourished female can lay up to 300 eggs in her lifetime.

In warm weather, nymphs develop into adults in about two months. Although bed bugs are thought not to carry any harmful human diseases, their bites are very irritating.

A honey bee stinger (Apis mellifera). Female worker bees rarely sting unless their hives are threatened. When they do, the stinger slices the skin of the victim and sacks of venom attached to the stinger are released.

Barbs on the stinger anchor it so securely in the skin of the victim that the stinger separates from the abdomen of the bee, killing it.

Most people are uncomfortable from a sting for an hour or so, but those who have severe allergic reactions to the venom may need immediate treatment for anaphylactic shock.

Bird mite between feather barbs.

Aquatic black fly larvae (Simulium sp.) emerge from eggs and attach themselves to aquatic vegetation and rocks. Most black fly larvae nymphs are filter feeders. Larvae pass through six stages before reaching the pupal stage. Adults emerge from the pupal case through a slit and float to the surface on a bubble of air.

The adults are considered a human pest in some areas of the U.S. and Canada. The adults are similar to eye gnats and fly around human faces. Adult black fly females lay their eggs in slow moving waters. Female black flies feed on blood and males feed mainly on nectar.

Conidia (asexual spores) are produced on the conidiophores (fruiting structures/sporangia). This genus causes skin infections in burn victims and the fungal lung infection aspergillosis (secondary infection to AIDS).

Clotting is the body's normal response to a bleeding injury. To control bleeding from vessels larger than capillaries a clot must form at the injury site. Platelets, one of the three main cellular components of human blood, serve as the body's first line of defense to prevent blood loss. When an injury such as a cut occurs, platelets become activated platelets.

They change their shape, become sticky and build up on a blood vessel wall to form a plug. Platelets are also involved in the secretion of chemical platelet factors into the blood plasma.

In a complex series of reactions fibrinogen is converted into fibrin, an insoluble protein that forms an intricate network of tiny threads called fibrils. Blood cells and plasma are tangled in the network of fibrils to form the clot.

Activated (pink/purple) and non-activated platelets (orange) with channels of the open canalicular system (OCS). Platelets are cell fragments in the blood that play an essential role in blood clotting and wound repair.

Platelets can also activate certain immune responses. Platelets are formed in the red bone marrow, lungs, and spleen by fragmentation of very large cells known as megakaryocytes. Platelets in the blood are small oval disks and are termed non-activated platelets or thrombocytes.

A bloodworm is an aquatic insect larval stage of a non-biting midge (Chironomus tetans). The head has modified mouthparts for filtering small food organisms. Bloodworms frequently build tubes of mud around themselves, which may be attached to stones.

The bloodworm has an iron-porphyrin protein, respiratory pigment in its blood and tissue fluids (red) that corresponds to hemoglobin in vertebrates. This larva is important in the aquatic food chain.

Adult sheep bot flies (Oestrus ovis) do not oviposit (eggs laid in the host by the adult female). Larvae hatch within the female fly; she deposits them in or near the host's nostrils. The larvae have special hooks to anchor in the nasal passages and frontal sinuses.

Larvae feed on the mucosal tissue. The larvae remain in the sinuses for 8 to 10 months and then are sneezed out of the nostrils. Fully-grown larvae exit the nostrils and pupate in debris on the soil for 3 to 6 weeks or more, depending on temperature.

Bracket fungus basidiocarp (fruiting body) lower surface showing skeletal (edge) and generative hyphae (gill, spore producing). Bracket fungi are so named because they occur as individual fruiting bodies (mushrooms) in a grouping or pattern known as a "bracket".

They generally cover a tree trunk in separate or connected horizontal rows. Oyster mushrooms are an example of delicate, edible bracket fungi, but shapes of other species vary from papery thin to thick, woody and large.

Brown dog tick (Rhipicephalus sanguineus). The brown dog tick is small, red-brown arachnid (called the red dog tick outside the U.S.) with specialized mouthparts for sucking blood. It is found on dogs, in kennels and houses, and occasionally on other animal wildlife. In the U.S., the brown dog tick is a vector of disease in dogs.

Unlike most other ticks, it can complete its entire life cycle indoors, allowing it to establish populations in cold climates. Because of this, it is found in much of the world.


Characteristic features are the six eyes arranged in three pairs at the front of the head and the fiddle-shaped marking on the back. The brown recluse spider is often called the violin spider or fiddleback spider.

The bite of this spider is nasty and results in open, ulcerating sores. Left untreated, such bites often become infected and significant tissue necrosis can occur.

Butterfly proboscises are slender, tubular feeding structures. Culminating in a sharp, beak-like tip, the proboscis works like a straw through which a butterfly drinks its food. When a butterfly finds food, it first unfurls its mouthparts and then zips them together to form a channel.

The proboscis is particularly well adapted for reaching into flowers for nectar and for piercing fruit with its sharp tip. When a butterfly is not feeding, it keeps its proboscis curled between its palpi (which are a pair of organs located on the front of an adult butterfly face).