Acromis spinifex
Encyclopedia
Acromis spinifex is a species
of tortoise beetle
from South America
. The males have enlarged elytra which are probably used in male–male combat, while females are among the few tortoise beetles to show maternal care
of their offspring.
, from Trinidad and Tobago
and Venezuela
in the north to Peru
, northern Argentina
and Paraguay
in the south.
. The elytra
of males extend sideways and forwards to form flattened plates. Other species in the genus have been studied more closely, and they have been observed to engage in male–male combat, in which the flattened parts of the elytra are often pierced; such holes are frequently found in museum specimens
of Acromis.
Males are 10.9–12.7 mm (0.429133858267717–0.5 ) long and 8.7 millimetre wide, while females are slightly smaller, 9.7 millimetre long and 8.3 millimetre wide.
, typically Ipomoea
species such as the sweet potato
, Ipomoea batatas. Predators of A. spinifex include the shield bugs Stiretrus smaragdatus and S. decastigma.
Acromis spinifex is unusual among tortoise beetles in that it practises parental care
of its offspring. All stages of the young beetle are guarded by the female, from the egg
to the pupa
. The female lays a mass of 15 white, oblong eggs, which are glued together and attached to the midrib of a leaf of the host plant. Each egg is 1.4 millimetre long by 0.7 millimetre wide. The final larva
l instar
is 4.8 millimetre long, and yellowish, with a brown head and brown legs. Reports of paternal care derive from an illustration published in 1939 which wrongly showed a male guarding eggs.
by Carl Linnaeus in his 1763 work Centuria Insectorum
, under the name Cassida spinifex. In 1837, it was made the type species
of the new genus Acromis by Louis Chevrolat
. One lectotype
and one paralectotype were designated in 1999 and are deposited in the Naturhistoriska Riksmuseet
in Stockholm
, Sweden
.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of tortoise beetle
Tortoise beetle
The tortoise beetles are an artificial grouping of tribes within the leaf beetle subfamily Hispinae. In past classifications, they have been variously placed as a family or a subfamily ; when it was recognized that this group was not monophyletic, it was split and the resulting tribes were...
from South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
. The males have enlarged elytra which are probably used in male–male combat, while females are among the few tortoise beetles to show maternal care
Parental investment
In evolutionary biology, parental investment is any parental expenditure that benefits one offspring at a cost to parents' ability to invest in other components of fitness...
of their offspring.
Distribution
Acromis spinifex is found across South AmericaSouth America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
, from Trinidad and Tobago
Trinidad and Tobago
Trinidad and Tobago officially the Republic of Trinidad and Tobago is an archipelagic state in the southern Caribbean, lying just off the coast of northeastern Venezuela and south of Grenada in the Lesser Antilles...
and Venezuela
Venezuela
Venezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...
in the north to Peru
Peru
Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....
, northern Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
and Paraguay
Paraguay
Paraguay , officially the Republic of Paraguay , is a landlocked country in South America. It is bordered by Argentina to the south and southwest, Brazil to the east and northeast, and Bolivia to the northwest. Paraguay lies on both banks of the Paraguay River, which runs through the center of the...
in the south.
Description
As with other species in the genus Acromis, A. spinifex shows conspicuous sexual dimorphismSexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
. The elytra
Elytron
An elytron is a modified, hardened forewing of certain insect orders, notably beetles and a few of the true bugs ; in most true bugs, the forewings are instead called hemelytra, as only the basal half is thickened while the apex is membranous...
of males extend sideways and forwards to form flattened plates. Other species in the genus have been studied more closely, and they have been observed to engage in male–male combat, in which the flattened parts of the elytra are often pierced; such holes are frequently found in museum specimens
Zoological specimen
A zoological specimen is an animal or part of an animal preserved for scientific use.Various uses are : to verify the identity of a , to allow study, increase public knowledge of zoology.Zoological specimens are extremely diverse...
of Acromis.
Males are 10.9–12.7 mm (0.429133858267717–0.5 ) long and 8.7 millimetre wide, while females are slightly smaller, 9.7 millimetre long and 8.3 millimetre wide.
Ecology and life cycle
The host plants of Acromis spinifex are plants in the family ConvolvulaceaeConvolvulaceae
Convolvulaceae, known commonly as the bindweed or morning glory family, are a group of about 60 genera and more than 1,650 species of mostly herbaceous vines, but also trees, shrubs and herbs.- Description :...
, typically Ipomoea
Ipomoea
Ipomoea is the largest genus in the flowering plant family Convolvulaceae, with over 500 species. Most of these are called "morning glories", but this can refer to related genera also. Those formerly separated in Calonyction are called "moonflowers"...
species such as the sweet potato
Sweet potato
The sweet potato is a dicotyledonous plant that belongs to the family Convolvulaceae. Its large, starchy, sweet-tasting, tuberous roots are an important root vegetable. The young leaves and shoots are sometimes eaten as greens. Of the approximately 50 genera and more than 1,000 species of...
, Ipomoea batatas. Predators of A. spinifex include the shield bugs Stiretrus smaragdatus and S. decastigma.
Acromis spinifex is unusual among tortoise beetles in that it practises parental care
Parental investment
In evolutionary biology, parental investment is any parental expenditure that benefits one offspring at a cost to parents' ability to invest in other components of fitness...
of its offspring. All stages of the young beetle are guarded by the female, from the egg
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
to the 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...
. The female lays a mass of 15 white, oblong eggs, which are glued together and attached to the midrib of a leaf of the host plant. Each egg is 1.4 millimetre long by 0.7 millimetre wide. The final 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...
l 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...
is 4.8 millimetre long, and yellowish, with a brown head and brown legs. Reports of paternal care derive from an illustration published in 1939 which wrongly showed a male guarding eggs.
Taxonomic history
Acromis spinifex was first describedAlpha taxonomy
Alpha taxonomy is the discipline concerned with finding, describing and naming species of living or fossil organisms. This field is supported by institutions holding collections of these organisms, with relevant data, carefully curated: such institutes include natural history museums, herbaria and...
by Carl Linnaeus in his 1763 work Centuria Insectorum
Centuria Insectorum
is a 1763 taxonomic work by Carl Linnaeus, and defended as a thesis by Boas Johansson; which of the two men should be credited with its authorship has been the subject of some controversy. It includes descriptions of 102 new insect and crustacean species that had been sent to Linnaeus from...
, under the name Cassida spinifex. In 1837, it was made the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
of the new genus Acromis by Louis Chevrolat
Louis Alexandre Auguste Chevrolat
Louis Alexandre Auguste Chevrolat was a French entomologist, born 29 March 1799 at Paris and died16 December 1884 in the same city.In government service in Paris, this amateur entomologist studied, mainly, Coleoptera and birds...
. One lectotype
Lectotype
In botanical nomenclature and zoological nomenclature, a lectotype is a kind of name-bearing type. When a species was originally described on the basis of a name-bearing type consisting of multiple specimens, one of those may be designated as the lectotype...
and one paralectotype were designated in 1999 and are deposited in the Naturhistoriska Riksmuseet
Swedish Museum of Natural History
The Swedish Museum of Natural History , in Stockholm, is one of two major museums of natural history in Sweden, the other one being located in Gothenburg....
in Stockholm
Stockholm
Stockholm is the capital and the largest city of Sweden and constitutes the most populated urban area in Scandinavia. Stockholm is the most populous city in Sweden, with a population of 851,155 in the municipality , 1.37 million in the urban area , and around 2.1 million in the metropolitan area...
, Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
.