Gyrostigma rhinocerontis
Encyclopedia
Gyrostigma rhinocerontis (also known as the Rhinoceros stomach botfly) is the largest fly
species known in Africa
. It is a parasite of the Black Rhinoceros
and the White Rhinoceros
.
Because the fly depends on the rhinoceros for reproduction, its numbers declined steeply as the black and white rhinos faced extinction. Like the rhinoceros, it must once have spread across much of sub-Saharan Africa (outside of the Congo Basin), but is today restricted to the savanas of southern and eastern Africa.
The fly was discovered in the mid-19th century, initially from larvae within the stomach of a rhinoceros. A fuller explanation was given by Fritz Konrad Ernst Zumpt
in the mid-20th century. Despite being known for a long time, little is known about some aspects of their life, because they are difficult to observe in the wild as well as to breed in captivity. Only a few large museums have a specimen.
, the adult lays eggs on the host animal, in this case, near the horn of the rhinoceros or elsewhere on the head. The eggs are oblong and white. The eggs hatch after about six days, and the larva
e, about 0.1 inch long, burrow inside, and attach themselves to the stomach wall by spines and mouth-hooks. It feeds on the blood and tissue of the rhinoceros.
The larvae pass through three instar
s (developmental stages) while attached to the stomach. In the first instar, they are colored dark pink and are buried deep within mucosal folds of the stomach lining. In the second instar, the larvae are about 0.8 inches long, a paler shade of pink, and their spikes are more prominent. At this point only their front ends are imbedded into the folds. In the third instar, the larvae reach adult size, and are whitish to yellow with irregular brown spots. Their spikes form bands three or four rows wide. Rhinoceroses have been observed with large quantities of larvae in various stages.
When it is ready to pupa
te, it leaves the rhinoceros through the anus. The pupa are not, however, found within dung piles, so they either leave independently or burrow into the ground immediately after defecation. Pupation lasts six weeks, after which the adult fly emerges. The largest adults can reach 1.6 inches in length and have a wingspan of 2.8 inches. They resemble a black wasp
with an orange-red head and legs. The wings are brown to black, and are long enough that at rest they run nearly the entire length of the body. Their mouthparts are rudimentary, and they probably do not eat at all as adults.
The evidence is conflicting on what time of day they are active. David A. Barraclough believes that females are active during the day, when eggs are to be deposited on the hosts, while males are active at dawn and dusk, when mating occurs. The flies are airborne for only three to five days before expiring.
Fly
True flies are insects of the order Diptera . They possess a pair of wings on the mesothorax and a pair of halteres, derived from the hind wings, on the metathorax...
species known in Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
. It is a parasite of the Black Rhinoceros
Black Rhinoceros
The Black Rhinoceros or Hook-lipped Rhinoceros , is a species of rhinoceros, native to the eastern and central areas of Africa including Kenya, Tanzania, Cameroon, South Africa, Namibia, Zimbabwe, and Angola...
and the White Rhinoceros
White Rhinoceros
The White Rhinoceros or Square-lipped rhinoceros is one of the five species of rhinoceros that still exist. It has a wide mouth used for grazing and is the most social of all rhino species...
.
Because the fly depends on the rhinoceros for reproduction, its numbers declined steeply as the black and white rhinos faced extinction. Like the rhinoceros, it must once have spread across much of sub-Saharan Africa (outside of the Congo Basin), but is today restricted to the savanas of southern and eastern Africa.
The fly was discovered in the mid-19th century, initially from larvae within the stomach of a rhinoceros. A fuller explanation was given by Fritz Konrad Ernst Zumpt
Fritz Konrad Ernst Zumpt
Fritz Konrad Ernst Zumpt was a German entomologist who worked mainly in Africa . He is best known for his work on Diptera and the associations between insects and African mammals. Also for his work on myiasis.Amongst Zumpt’s works are...
in the mid-20th century. Despite being known for a long time, little is known about some aspects of their life, because they are difficult to observe in the wild as well as to breed in captivity. Only a few large museums have a specimen.
Life cycle
Like other botfliesBotfly
A botfly is any fly in the family Oestridae, which includes all the members of the former families Cuterebridae, Gasterophilidae, and Hypodermatidae. It is the only family of flies whose larvae live as obligate parasites within the bodies of mammals, with the exception of a few screwworm flies in...
, the adult lays eggs on the host animal, in this case, near the horn of the rhinoceros or elsewhere on the head. The eggs are oblong and white. The eggs hatch after about six days, and the larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e, about 0.1 inch long, burrow inside, and attach themselves to the stomach wall by spines and mouth-hooks. It feeds on the blood and tissue of the rhinoceros.
The larvae pass through three instar
Instar
An instar is a developmental stage of arthropods, such as insects, between each molt , until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or assume a new form. Differences between instars can often be seen in altered body proportions, colors, patterns, or...
s (developmental stages) while attached to the stomach. In the first instar, they are colored dark pink and are buried deep within mucosal folds of the stomach lining. In the second instar, the larvae are about 0.8 inches long, a paler shade of pink, and their spikes are more prominent. At this point only their front ends are imbedded into the folds. In the third instar, the larvae reach adult size, and are whitish to yellow with irregular brown spots. Their spikes form bands three or four rows wide. Rhinoceroses have been observed with large quantities of larvae in various stages.
When it is ready to pupa
Pupa
A pupa is the life stage of some insects undergoing transformation. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, going through four life stages; embryo, larva, pupa and imago...
te, it leaves the rhinoceros through the anus. The pupa are not, however, found within dung piles, so they either leave independently or burrow into the ground immediately after defecation. Pupation lasts six weeks, after which the adult fly emerges. The largest adults can reach 1.6 inches in length and have a wingspan of 2.8 inches. They resemble a black wasp
Wasp
The term wasp is typically defined as any insect of the order Hymenoptera and suborder Apocrita that is neither a bee nor an ant. Almost every pest insect species has at least one wasp species that preys upon it or parasitizes it, making wasps critically important in natural control of their...
with an orange-red head and legs. The wings are brown to black, and are long enough that at rest they run nearly the entire length of the body. Their mouthparts are rudimentary, and they probably do not eat at all as adults.
The evidence is conflicting on what time of day they are active. David A. Barraclough believes that females are active during the day, when eggs are to be deposited on the hosts, while males are active at dawn and dusk, when mating occurs. The flies are airborne for only three to five days before expiring.
External links
- Image of fly from Natural History Museum
- Image of maggot from Natural History Museum
- Online copy of Natural History article
- A Rhino's Strange Companions, an article on rhinoceros parasites from the David Sheldrick Wildlife Trust, Nairobi, Kenya