Insects – useful, troublesome, mysterious, scary, beautiful ... World champions in countless disciplines. But small and difficult to observe as well! Today, we can discover this world through movies, SEM photos or 3D models. However, meticulously detailed scientifically accurate models were created already between 1930 and 1955 at the Berlin Natural History Museums.
Alfred Keller working on the Fly model (ZM_B_III_635) by Unknown photographerMuseum für Naturkunde Berlin
The best works were created by Alfred Keller, a keen observer of nature, artisan, and inventor of innovative modeling techniques. Keller created works of a fascinating aesthetics that are at the same time scientifically highly accurate. The surviving models, mostly 30-40 cm in size, can still tell us engaging stories from the world of insects ...
Keller's insect models: House fly (1932) by Alfred Keller (MfN)Museum für Naturkunde Berlin
This model of a house fly (Musca domestica) is the result of over one year or hard work by Alfred Keller.
The house fly belong to the order "Diptera" ("two-wingers"). In these insect, the forewings (left) are complete, whereas the hindwings are reduced to small club-shaped structures called "halteres". You can see them as light, club- dumbbell-shaped structures in the lower center. When flying, these structures move in the opposite direction of the forewings, stabilizing the flight.
Each compound eye consists of about 4000 photoreceptor units (ommatidia). In the front you can see the short antennae, on the top three ocelli. The latter are found in most insects; their function is an area of active research.
On the feet we see two lighter cushion-like structures (pulvilli), which are covered with a large number of tiny hairs. These are highly adhesive and enable flies to walk on the ceiling or window panes. By the way: Flies can "taste" with their feet!
Keller's insect models: Model of fly metamorphosis (eggs, larvae, chrysalis) by Alfred Keller (MfN)Museum für Naturkunde Berlin
Female house flies lay up to 400 eggs into dead organic material such as decomposing plants, carrion or feces.
The larvae hatch within 12-24 hours, feedin on the decomposing material.
After moulting twice, the larvae turns into a small, darkish chrysalis. The metamorphosis takes between 3 and 8 days, after which the adult fly emerges.
Keller's insect models: Ant and louse by Alfred Keller (MfN)Museum für Naturkunde Berlin
Model of a maple aphid (Drepanosiphum) with a common red ant (Myrmica rubra). Aphids feed on plant sap, which is very rich in sugars, but has few proteins. The aphids remove the protein and release most of the sugars in the form of so-called "honeydew" secretions. When cars parked under trees become amazingly sticky: This was the action of the aphids, not the tree itself! Honey dew is the most important carbohydrate source of many ants. The relation between aphids and ants is often a mutualism: These ants protect the aphids against predators like ladybugs, even move them to new leaves, and actively milk the aphids by stroking them with their antennae.
Keller's insect models: The Brazilian treehopper (1953) by Alfred Keller (MfN)Museum für Naturkunde Berlin
The Brazilian treehopper (Bocydium globulare) is one of the most incredible animals of the world. In reality only about 6 mm large, it feeds on plant sap. Like other leafhoppers, it can jump explosively when threatened.
The scutum bears a most amazing structure with 2 spiked and 2 simple balls. Their function is not fully understood: Hypothesis range from camouflage to frightening or confusing predators.
Keller's insect models: Model of adult and larval potatoe beetle by Alfred Keller (MfN)Museum für Naturkunde Berlin
An adult potatoe beetle (Leptinotarsa decemlineata) with a larvae in the background. Introduced to Europe in 1922 from America, both larvae and adults feed on potatoe leaves, causing severe economical damages.
Both the Nazis under Hitler and the communist German Democratic Republic claimed, the Americans would drop potatoe beetles from airplanes as a biological weapon. The famous German poet Bertolt Brecht did believe this and wrote: "Die Amiflieger fliegen, silbrig im Himmelszelt, Kartoffelkäfer liegen, in deutschem Feld (American planes fly, silver-colored in the sky, Potatoe beetles lie, in German fields)." However, there is no evidence that this ever happened. Instead, there are plenty of examples, how invasive species can effect similar damages without any such support. But the old propaganda message is still widely and stubbornly believed. We are probably more willing to believe in the powers of war machines than accept the power of nature itself!
Keller's insect models: Model of a mosquito by Alfred Keller (MfN)Museum für Naturkunde Berlin
Female mosquito (Culex pipiens) in flight posture.
Only female mosquitoes draw blood from other animals with their proboscis. It is built from a sheath (consisting of the labium) which encloses 4 piercing mouthparts (two mandibles, two maxillae) and 2 hollowed mouthparts (the hypopharynx injects saliva, the labrum draws the blood).
Keller's insect models: Model of the metamorphosis stages of a true bug (Heteroptera,Pentatomidae, Sloe Bug = Dolycoris baccarum) by Alfred Keller (MfN)Museum für Naturkunde Berlin
Egg, larvae and adult of the Sloe Bug (Dolycoris baccarum). Whereas in some insect orders like beetles or butterflies larvae and adults are strongly dissimilar, and the larvae form a chrysalis to be fully transformed in a process called metamorphosis, the larvae of the true bugs (Heteroptera) and many other insect orders look immediately similar to the adults. They become more and more similar with each ecdysis (which occurs five times in the case of this species).
The Sloe Bug feeds on flowers and fruits of many species (especially from the rose family, like cherries or plums). Because when sucking plant saps it also injects saliva, the fruits often become unpalatable for humans.
Only the adults have fully developed wings.
Keller's insect models: The wheat weevil (1935) by Alfred Keller (MfN)Museum für Naturkunde Berlin
An insect model of the wheat weevil (Sitophilus granarius) created by Alfred Keller. This weevil is a constant follower of humankind since the early stone age and one of the most feared pests of stored products.
The chewing mouthparts are at the tip of elongated snout. The females eat tiny holes into grain kernels, lay an egg, and close the hole with a secreted substance. The whole development of the larvae occurs inside the kernel, until finally the fully developed beetle emerges from the hollowed-out kernel.
Keller's insect models: Model of the flour moth or meal moth ((Ephestia kuehniella), with caterpillar larvae, chrysalis and eggs. by Alfred Keller (MfN)Museum für Naturkunde Berlin
Life cycle of the Meal moth (Ephestia kuehniella). The female lays ...
... tiny eggs, which develop into ...
... a sizeable caterpillar larvae, which becomes ...
... a chrysalis in which the metamorphosis to the adult moth (the "imago") occurs.
Meal moths are frequent stored product pests. The larvae feed mainly on cereal products (flour, rolled oats, whole kernels, but also pasta). The adults can place several 100 eggs next to the tiniest of openings in packaging. Freshly hatched, the larvae are only 1 mm long and much thinner, being able to enter many resealable household packages through tiny openings that usually remain. After 40 days the larvae turns into a chrysalis, after another 10 the adult moth (which no longer feeds) emerges. (Model by Alfred Keller)
Keller's insect models: Model of a human flea by Alfred Keller (MfN)Museum für Naturkunde Berlin
A human flea, (Pulex irritans). These wingless insects are at most 3 mm long. Relative to their size, they have amazing jumping capabilites (18 cm high and 30 cm wide). Their narrow build enables them to move between the hairs of their host.
As a result of improved living conditions of humans, the human flea has become relative rare. Today, flea bites on humans often are the result of animal fleas, especially cat fleas!
Alfred Keller working on the Potatoe beetle (ZM_B_III_686) by Unknown photographerMuseum für Naturkunde Berlin
Insects are fascinating animals. Many strongly influence our lives in major ways. When we are enabled to study them in detail, they can tell us stories.
We consider Alfred Keller both as a talented and keen scientific observer and as an artist. He worked in close collaboration with another artist: Nature itself.
Text: Alice Chodura, Gregor Hagedorn (Museum für Naturkunde Berlin)
Photos: Carola Radke, Hwa Ja Götz (Museum für Naturkunde Berlin)
Contributors: Dr. Johannes Frisch, Linda Gallé (Museum für Naturkunde Berlin)