PHEROMONE COMMUNICATION IN FEATHER-FEEDING WING LICE (INSECTA: PHTHIRAPTERA)

Abstract

Pheromone communication is central to the life history of insect parasites. Determining how pheromones affect parasite behavior can provide insights into host-parasite interactions and suggest novel avenues for parasite control. Lice infest thousands of bird and mammal species and feed on the host's feathers or blood. Despite the pervasiveness of lice in wild populations and the costs they exact on livestock and poultry industries, little is known about pheromone communication in this diverse group. Here, we test for pheromone communication in the wing lice (Columbicola columbae) of Rock Doves (Columba livia). Wing lice spend the majority of their lives on bird flight feathers where they hide from host preening by inserting their bodies between coarse feather barbs. To feed, wing lice must migrate to bird body regions where they consume the insulating barbs of contour feathers. We first show that wing lice readily form aggregations on flight feathers. Next, using a Y-tube olfactometer, we demonstrate that wing lice use pheromone communication to move toward groups of nearby conspecifics. This pheromone is likely an aggregation pheromone, as wing lice only produce the pheromone when placed on flight feathers. Finally, we found that when forced to choose between groups of male and female lice, male lice move toward male groups and females toward female groups, suggesting the use of multiple pheromones. Ongoing work aims to determine the chemical identity and function of these pheromones.

Keywords: Columbicola columbae; Aggregation behavior; Chemical communication; Pheromone; Rock Dove; Wing lice.

Figure 1.

Scanning electron micrograph of a typical aggregation of wing lice (Columbicola columbae) found inserted between the barbs of a Rock Dove flight feather (Columba livia).

Figure 2.

Experimental setup for the Y-tube olfactometer. Humidified and purified air was sent through the apparatus at 0.1 L/min. For each trial, an individual louse was placed on a cardboard track and a choice was recorded when it traveled 1.5 cm up either arm. The experimental chamber contained groups of wing lice placed in an empty chamber, on body feathers, or on wing feathers. The control chamber was empty or contained body or wing feathers, respectively.

Figure 3.

Location of all wing lice (Columbicola columbae) found on Rock Dove (Columba livia) wing and tail feathers. Each flight feather was divided into 3 equal regions (proximal, central, and distal) and the position of all wing lice was recorded during a 2- to 3-min visual examination of each bird (n = 13 birds). (A) Percentage of all lice found in each region on all wing feathers (remiges) and tail feathers (rectrices). (B) Mean number of lice (±SE) found on proximal, central, and distal regions of flight feathers. Lice showed a significant preference for the central regions of wing and tail feathers (different letters represent a significant difference between means; analysis of variance with posthoc Tukey–Kramer tests).

Figure 4.

Histogram showing the distribution of louse group sizes (Columbicola columbae) on Rock Dove (Columba livia) flight feather regions. Each feather was divided into 3 regions and louse distribution was recorded on each bird using a 2- to 3-min visual examination (n = 13 birds). Only feather regions containing lice are included (n = 466 regions of 2,028 examined). Over 50% of all inhabited feather regions harbored ≥3 lice.