signal fly

(Rivellia spp.)

signal fly (Rivellia sp.)
Photo by Greg Watson

Rivellia is a genus of small flies in the family Platystomatidae (signal flies). There are at least 140 Rivellia species worldwide, 34 species in North America north of Mexico, and at least 14 species in Minnesota.

Rivellia adults are found on tree trunks and on foliage. They are attracted to flowers, decaying fruit, dung, and decomposing snails. Larvae are associated with the living and decaying root nodules of legumes and the roots and flowers of other plants. One species, the soybean nodule fly, has shifted from natural legume hosts to specialize in cultivated soybean crops.


Rivellia signal flies are very small, with a body length of just 116 to ¼ (1.8 to 6.0 mm). The genus is easy to recognize by the pattern of dark markings on the wings. Identification to the species level by photograph is difficult, sometimes relying on obscure features such as the direction of the hairs (setae) on the fourth abdominal segment.

When viewed from the side the face is concave and the back of the head is convex. The compound eyes do not meet at the top of the head on either sex. The antennae have three segments. The third segment is long and has a short, feather-like (plumose), forward-pointed bristle (arista) on the upper side. The wings are clear with four dark bands. The fourth segment (tibia) on the middle legs has a single long spur at the tip.


Distribution Map



24, 27, 29, 30, 82.

A revision of the flies of the genus Rivellia (Otiidae, Diptera) of America north of Mexico Ryoji Namba. 1956. United States National Museum.



Diptera (flies)  




  No Rank Eremoneura  
  No Rank Cyclorrhapha  
  Zoosection Schizophora (schizophora flies)  
  Zoosubsection Acalyptratae (acalyptrate flies)  


Tephritoidea (fruit, signal, and picture-winged flies)  


Platystomatidae (signal flies)  



Subordinate Taxa


signal fly (Rivellia cognata)

signal fly (Rivellia colei)

signal fly (Rivellia cognata)

signal fly (Rivellia coquilletti)

signal fly (Rivellia flavimana)

signal fly (Rivellia melliginis)

signal fly (Rivellia metallica)

signal fly (Rivellia munda)

signal fly (Rivellia pallida)

signal fly (Rivellia steyskali)

signal fly (Rivellia variabilis)

signal fly (Rivellia viridulans)

signal fly (Rivellia winifredae)

soybean nodule fly (Rivellia quadrifasciata)






Common Names


This genus has no common name. The common name of the family Platystomatidae is signal flies, and it is applied here for convenience.











A large bristle on the upper side of the third segment of the antenna of a fly.



A stiff, hair-like process on the outer surface of an organism. In Lepidoptera: A usually rigid bristle- or hair-like outgrowth used to sense touch. In mosses: The stalk supporting a spore-bearing capsule and supplying it with nutrients. Plural: setae. Adjective: setose.



The fourth segment of an insect leg, after the femur and before the tarsus (foot).






Visitor Photos

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Greg Watson

    signal fly (Rivellia sp.)      








Visitor Videos

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Other Videos
  SIGNAL FL, Rivellia
Rob Curtis

Nov 8, 2019

SIGNAL FLY, Rivellia. McClaughery Springs FP, IL 7/11/2019.

  Meet Rivellia, a Platysomatid Fly
Carl Barrentine

Jun 25, 2017

This short film introduces one of our local Platysomatid flies, a species in the genus Rivellia. Filmed at the Turtle River State Park, Arvilla, North Dakota (25 June 2017).

  Signal Fly (Platystomatidae: Rivellia) on Leaf
Carl Barrentine

Jun 12, 2010

Photographed at Turtle River State Park, North Dakota (11 June 2010).

  Signal Flies (Platystomatidae: Rivellia) Male and Female
Carl Barrentine

Jun 24, 2010

"And then there is the world of little things, seen all too seldom. Many children, perhaps because they themselves are small and closer to the ground than we, notice and delight in the small and is easy to share with them the beauties we usually miss... because we move too hastily, seeing the whole and not its parts." --Rachel Carson The female leads and male follows. They have just finished mating. Photographed at Turtle River State Park, North Dakota (24 June 2010).




Visitor Sightings

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  Greg Watson

Location: La Crescent, MN

in my backyard

signal fly (Rivellia sp.)







Created: 8/24/2021

Last Updated:

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