Insect guide > Flies > Fruit and Gall Flies

Fruit and Gall Flies


(Family Trypetidae.)
Most of the flies of this family are rather small, although some are above medium size. They are of very striking appearance and interesting habits. They vary from light yellow in color to dark brown or nearly black, and the body is frequently curiously spotted in the lighter specimens. The wings are also beautifully banded and marked. The group is a large one and is well represented in the United States, many genera and species occurring with us.

The Trypetid flies in their early stages live in fruits or in the stems of plants, producing galls. The so-called apple maggot of the Northeastern States, an insect which is especially abundant in Maine and New Hampshire, is the larva of Rhagdetis pomonella. It eats into the pulp of apples, boring tunnels in all directions through the fruit. It is said especially to attack the earlier ripening apples. When full grown it drops to the ground and transforms within the last larval skin.

The adult insect is a black and white fly with banded wings. One of the large round galls which occurs upon the stems of goldenrod is made by one of these flies known as Eurosta asteris. There are sometimes two of these galls on the same stalk, and they are most conspicuous in the winter time when there are no leaves on the plant. If one cuts open one of these galls it is found to be full of a pithy solid mass, in the center of which is the plump, white maggot of this fly. A famous member of this family is known as Ceratitis capitata, which damages peaches and other fruit in different parts of the world. It is common and injurious in Bermuda, but, fortunately, has not established itself in the United States. Another Trypetid fly which does great damage is Anastrepha ludens, the larva of which is known as the Morelos orange fruit worm. It bores into the pulp of oranges, and renders them unfit for eating purposes. The larva of Trypeta fratria Loew mines the leaves of parsnip in many parts of the country.