Gall Midges

Top Photo: Cypress flower midge galls on bald cypress needles (November).

When female cypress flower gall midges emerge in the spring they mate and immediately lay eggs on fresh green needles of bald cypress trees. The feeding larvae which hatch from the eggs stimulate the needles into forming flower shaped galls on their surfaces.

Cypress flower gall midge galls during summer.

The galls look very much like tiny fungi, but inside each one of the little “mushrooms” is a larva of a cypress flower gall midge. The larva will feed, grow and pupate within this protective case.

Resembles small mushroom.
In fall, when needles turn brown and drop.

According to North Carolina State Extension Publications “It is likely that we have only one generation [of cypress flower gall midge] per year in North Carolina.” In fall, the needles and attached galls, drop to the ground. The 1mm to 2mm larvae within the galls may overwinter as such in the leaf liter below the tree and pupate in spring. However, the galls pictured here contain what looks like pupae not larvae (I’ve sliced into the galls to get the photos).

Gall sliced open to reveal pupa.
Pupa removed from gall with part of attached gall flesh.

The adult cypress flower gall midges are tiny flies (Taxodiomyia cupressi) about 1/8 inch long. They resemble mosquitoes, but do not have the long proboscis for drilling into human skin and sucking blood as do their notorious disease spreading relatives.

As mentioned, cypress flower gall midge galls are somewhat flower-shaped. A similar midge, and close relative of the cypress flower gall midge associated with bald cypress, is the cypress twig gall midge (Taxodiomyia cupressiananassa). It too lays eggs on the bald cypress, this time on the base of the cypress leaflets. Its galls are globular in shape, and there may be multiple larvae inside each gall.

Cypress twig gall midge galls.
Cypress twig gall midge gall.
Cypress twig gall cut open to reveal multiple chambers inside.
Close-up of same gall (arrow points to cypress twig gall midge larva).

There are two generations per season of cypress twig gall midge. The first, the emerging adults from the previous year, and their offspring later in the season.

Both bald cypress and pond cypress host these two midge species. We have only bald cypress in and around our wetland. The other, somewhat look-alike, deciduous conifer growing in close proximity to the many planted bald cypress we have in and around our wetland is dawn redwood. I’ve not observed galls of any type on redwood.

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