Rhagoletis juglandis

Rhagoletis juglandis
Scientific classification edit
R. juglandis
Binomial name
Rhagoletis juglandis
(Cresson, 1920)

Rhagoletis juglandis, also known as the walnut husk fly, is a species of tephritid or fruit fly in the family Tephritidae. It is closely related to the walnut husk maggot Rhagoletis suavis (Loew, 1862). This species of fly belongs to the R. suavis group, which has a natural history consistent with allopatric speciation. The flies belonging to this group are morphologically distinguishable.

The adult form of this fly is around 4 mm long. R. juglandis are distributed in Arizona, California, Texas, Kansas, and Mexico. The species infests the fruits of several species of walnut trees including Juglans regia (the English or Persian walnut), Juglans rupestris (a species of walnut indigenous to Arizona and Texas), Juglans hindsii (the California black walnut), and the Arizona walnut Juglans major.

The larvae are small and infest walnut fruits, having hatched from eggs laid by adult females under the surface of the husk of the walnut. The insect overwinters as a pupa in the soil, and adults emerge in mid to late summer. R. juglandis engages in superparasitism, during which conspecifics infest the same host, even when there are still uninfested hosts available.

Although courtship behavior is rare in the Rhagoletis genus, male flies demonstrate low-frequency wing vibration, accompanied by airborne infrasound; they also turn their wing edges upward. R. juglandis participate in a resource-defense mating system. Females follow resource-based cues such as ripeness (color), whereas males follow females for more opportunities to mate. The flies also respond to sex ratio to alter the amount of time that copulation takes. When male density is high, copulation times are longer.


R. juglandis was first described by E.T. Cresson, Jr. in 1920 from material from the exocarp of fruit of Juglens regia (the English or Persian walnut tree) in Arizona. The species was first named the black walnut fly in literature. This served to differentiate it from the walnut husk maggot Rhagoletis suavis. However, the common name walnut husk fly was later proposed and accepted for this species.[1]

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