Galls or cecidia are a kind of swelling growth on the external tissues of plants, fungi, or animals. Plant galls are abnormal outgrowths of plant tissues, similar to benign tumors or warts in animals. They can be caused by various parasites, from viruses, fungi and bacteria, to other plants, insects and mites. Plant galls are often highly organized structures so that the cause of the gall can often be determined without the actual agent being identified. This applies particularly to some insect and mite plant galls. The study of plant galls is known as cecidology.
Thrips are minute, slender insects with fringed wings and unique asymmetrical mouthparts. Different thrips species feed mostly on plants by puncturing and sucking up the contents, although a few are predators. Entomologists have described approximately 6,000 species. They fly only weakly and their feathery wings are unsuitable for conventional flight; instead, thrips exploit an unusual mechanism, clap and fling, to create lift using an unsteady circulation pattern with transient vortices near the wings.
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 usually only 2–3 mm (0.079–0.118 in) in length; many are less than 1 mm (0.039 in) long. They are characterised by hairy wings, unusual in the order Diptera, and have long antennae. Some Cecidomyiids are also known for the strange phenomenon of paedogenesis in which the larval stage reproduces without maturing first. In some species, the daughter larvae consume the mother, while in others, reproduction occurs later on in the egg or pupa.
Opilioacaridae is the sole family of mites in the order Opilioacarida, made up of about 13 genera. The mites of this family are rare, large mites, and are widely considered primitive, as they retain six pairs of eyes, and abdominal segmentation. They have been historically been considered separate from other mites belonging to Acariformes and Parasitiformes, but are now generally considered a subgroup of Parasitiformes based on molecular phylogenetics.
Cecidophyopsis ribis is an eriophyid mite which is best known for being a plant parasite, a pest of Ribes species, the genus that includes gooseberries and blackcurrants.
Muehlenbeckia complexa, commonly known as pōhuehue, although this name also applies to some other climbers such as Muehlenbeckia australis.
Aceria is a genus of mites belonging to the family Eriophyidae, the gall mites. These tiny animals are parasites of plants. Several species can cause blistering and galls, including erineum galls. A few are economically significant pests, while others are useful as agents of biological pest control of invasive plants such as rush skeletonweed, creeping thistle, and field bindweed.
Eriophyes is a genus of acari that forms galls, specially on trees of the family Rosaceae. Some are called blister mites. The blue butterfly Celastrina serotina has been reported to feed on these galls and also on the mites, making it one of the uncommon carnivorous Lepidoptera.
Cynips is a genus of gall wasps in the tribe Cynipini, the oak gall wasps. One of the best known is the common oak gall wasp, which induces characteristic spherical galls about two centimeters wide on the undersides of oak leaves.
Acalitus is a genus of mites in the family Eriophyidae. These cosmopolitan, microscopic arthropods form galls on various plants, and some species such as Acalitus essigi and Acalitus vaccinii are pests of agricultural significance associated with berry crops. This genus includes the following species:
Cynipini is a tribe of gall wasps. These insects induce galls in plants of the beech and oak family, Fagaceae. They are known commonly as the oak gall wasps. It is the largest cynipid tribe, with about 936 to 1000 recognized species, most of which are associated with oaks. The tribe is mainly native to the Holarctic. Cynipini wasps can act as ecosystem engineers. Their galls can become hosts of inquilines, and the wasps themselves are hosts to parasitoids.
Aculops is a genus of mites that belongs to the family Eriophyidae that live as plant parasites. Some species, such as Aculops lycopersici, are severe crop or ornamental pests, while Aculops ailanthii is being considered as biocontrol for the extremely invasive tree-of-heaven in North America. Very little is known about this genus, with new species constantly being discovered even in well covered regions such as New Zealand.
Phyllocoptes goniothorax is a species of mite belonging to the genus Phyllocoptes, which causes galls on the leaves of hawthorns. It was first described by Alfred Nalepa in 1889.
Acalitus brevitarsus is an eriophyid mite which induces domed, blister like swellings, known as galls, on some species of alder.
Synergus japonicus is a species of gall wasp in the family Cynipidae. Whereas most gall wasps create the galls in which they live, Synergus japonicus is an inquiline species, living in the gall created by another species of wasp. It is native to Japan, China and Russia.
Acalitus plicans is an eriophyid mite which causes galls on beech. It is found in Europe and was first described by the Austrian zoologist Alfred Nalepa in 1917.
Acalitus stenaspis is an eriophyid mite which causes galls on beech. It is found in Europe and was first described by the Austrian zoologist Alfred Nalepa in 1891.
Acalitus calycophthirus is an eriophyid mite which causes big bud galls on birch twigs. It is found in Europe and was first described by the Austrian zoologist, Alfred Nalepa in 1891.
Aceria elongata, the crimson erineum mite, is a species of eriophyid mite. This microscopic organism induces erineum galls on the upper leaf surfaces of sugar maple, and is known from the east coast of United States and Canada.
