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Insect Galls

Galls are “abnormal” structures that develop in the cells, tissues, or organs of a plant ONLY when it is colonized by certain parasitic organisms such as bacteria, fungi, nematodes, mites, or insects.   These gall-makers are collectively known as cecidozoa.   They usually secrete enzymes or plant hormones that stimulate hypertrophy (over-growth) and/or hyperplasy (cell proliferation) in their host plant.   The resulting structures are quite distinctive and highly species-specific.

Color photos of Common Galls

Cecidozoa – The Gall Makers

Many types of organisms are capable of producing galls.   Examples include:

A.   Nematodes (phylum Aschelminthes)
B.   Mites (class Acarina)
C.   Beetles (order Coleoptera)
D.   Psyllids (order Homoptera)
E.   True bugs (order Hemiptera)
F.   Wasps (order Hymenoptera)
G.   Flies (order Diptera)

Cecidocole Communities

A plant gall may be the center of a whole group of living organisms that interact with one another as a tiny ecological community.   In addition to the host plant and the gall-maker, this microcosm may include inquilines who live with the gall-maker, cecidophags who feed on the gall tissue, and sucessori who move into the gall and use it for shelter after the gall-maker moves out.   In addition, there may be predators and parasites of the gall-maker, the inquilines, the cecidophags, and the sucessori.   The predators and parasites may even have their own hyperparasites!   All of these animals are part of an interrelated food web — a cecidocole community.