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A gall-inducing insect is any insect that can cause the growth of galls within
A gall-inducing insect is any insect that can cause the growth of galls within plant
Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclud ...
s. There are several groups of insects that meet this description. They include the gall wasp
Gall wasps, also incorrectly called gallflies, are hymenopterans of the family Cynipidae in the wasp superfamily Cynipoidea. Their common name comes from the galls they induce on plants for larval development. About 1,300 species of this generall ...
s, scales, gall midge
Cecidomyiidae is a family of flies known as gall midges or gall gnats. As the name implies, the larvae of most gall midges feed within plant tissue, creating abnormal plant growths called galls. Cecidomyiidae are very fragile small insects us ...
s, aphid
Aphids are small sap-sucking insects and members of the superfamily Aphidoidea. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white woolly aphids. A t ...
s, psyllid
Psyllidae, the jumping plant lice or psyllids, are a family of small plant-feeding insects that tend to be very host-specific, i.e. each plant-louse species only feeds on one plant species (monophagous) or feeds on a few closely related plants ...
s and certain species of leafminer
A leaf miner is any one of numerous species of insects in which the larval stage lives in, and eats, the leaf tissue of plants. The vast majority of leaf-mining insects are moths (Lepidoptera), sawflies ( Symphyta, the mother clade of wasps) ...
flies
Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced ...
.
Galls are growth deformities induced in certain plants by various insects which are mostly species-specific. Galls induced by insects can be viewed as an extended phenotype
In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological proper ...
of the inducing insect, and gall-inducing insects specialize on their host plants, often to a greater extent than insects that feed on the same plant without creating galls.
The gall's form or type depends on what organism is attacking the plant and where the plant is being attacked.
Based on the form, there are two classification systems used to identify the cause of galls: causative agents located outside plant tissues, and those agents located inside plant tissues.
Causative outside agents include:
* ''Krebs gall'' is caused by surface agents.
* ''Filz gall'' is caused by agents among surface hairs.
* ''Fold/roll gall'' is caused by agents within turned-over leaf blades.
* ''Pouch gall'' is caused by agents within a cup-like structure that occurs when opposite ends of the infected structure arch upward and form a spherical oval.
Causitive inside agents include:
* ''Covering gall'' is caused by agents embedded within a gall when plant tissues rise up and surround the parasite.
* ''Lysenchyme gall'' is caused by agents that sink into the plant when the plant cells dissolve away and close around the parasite.
* ''Mark gall'' is caused by agents burrowing within plant tissue before gall develops.
This symbiotic
Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...
relationship is rather one-sided, with not much research verifying any benefit given to the plant species; therefore such insects are most likely parasite
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...
s of their host plant. The insect that causes the gall formation gets an entire microenvironment or microhabitat
In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...
provided to it, safe from climate and predation, to grow within, and with a rich supply of food formed within the gall for the insect to feed upon.
Ecologically, gall-inducing insects, because of their creation of a microhabitat
In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...
, are often attacked by parasitoid
In evolutionary ecology, a parasitoid is an organism that lives in close association with its host (biology), host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionarily stable str ...
or inquiline
In zoology, an inquiline (from Latin ''inquilinus'', "lodger" or "tenant") is an animal that lives commensally in the nest, burrow, or dwelling place of an animal of another species. For example, some organisms such as insects may live in the h ...
insects that take advantage of the excess resources the gall-inducer causes the plant to create, often leading to more biodiversity
Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...
in the ecosystem than what would exist without the presence of gall-inducers. Thus gall-inducing insects are examples of ecosystem engineer
An ecosystem engineer is any species that creates, significantly modifies, maintains or destroys a habitat. These organisms can have a large impact on species richness and landscape-level heterogeneity of an area. As a result, ecosystem enginee ...
s.
References
Sources
* Darlington, Arnold (1975) ''The Pocket Encyclopaedia of Plant Galls in Colour''. Poole: Blandford Press. . {{Insect-stub