Rhagoletis juglandis

Rhagoletis juglandis
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Diptera
Family:	Tephritidae
Genus:	Rhagoletis
Species:	R. juglandis
Binomial name
Rhagoletis juglandis Cresson, 1920[1]

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.