Host-Parasitoid Relationship between Apis mellifera (Linnaeus, 1758) and Senotainia tricuspis (Meigen, 1838) (Diptera, Sarcophagidae): Fly Aggression Behavior and Infestation Rates of Senotainiosis

Abstract

Senotainia tricuspis (Meigen, 1838) is a Sarcophagid dipteran endoparasitoid of Apis mellifera L., and myiasis, caused by this fly, is reported in several European, North African and Middle Eastern countries. Nevertheless, very little knowledge concerning the aggression and parasitisation behavior of S. tricuspis toward A. mellifera is available in the scientific literature, and the temporal pattern of aggression remains unclear. The aim of this investigation was to describe the aggressive behavior of S. tricuspis and to provide data on pupation and adult emergence in order to identify further tools for the control of senotainiosis in beekeeping. Data were collected in an apiary in Pisa province (Tuscany, Italy), where observations of aggressive behavior were conducted indirectly by using a VHS camera and also directly by an observer. Four behavioral categories of the attack were described. A total of 55 aggressions, 21 beecatchers, 104 chases and 6 parasitization events were recorded with the camera. Slow-motion recording analyses of the parasitization episodes resulted in contact of at least 1/6 s between the parasitoid and the host. Through four days of direct observations, a total of 1633 aggression events were recorded. The daily temporal pattern of the number of aggressions showed two main peaks: one during the morning hours (i.e., from 10:00 to 11:00) and one in the afternoon (i.e., from 15:00 to 17:00). The morphometric data on the first-instars of S. tricuspis allowed us to hypothesize a penetration in the bee through its prothoracic spiracle as a modality of entrance in the host body. Third-instars successfully pupate when sinking in topsoil or clay soil, and adults emerge when left to a 4 °C overwintering period of six months. Furthermore, the high mortality rate of those larvae that did not sink and did not pupate successfully suggests that reaching a certain depth in the soil is a determining factor for larvae survival and that mulch and/or minimum soil tillage could prevent severe senotainiosis in apiaries.

Keywords: behavioral observations; dipteran endoparasitoid; emerging adults; honey bee disease; infestation rate; parasitization; pupation.

Figure 1

Temporal pattern of S. tricuspis infestation rates in honey bee hives, from June to November 2004 and 2005, in an apiary in Pisa province, Italy.

Figure 2

A sequence of a parasitization event, detected through video-recording analysis, showing the four different behavioral categories: (a) Aggression: the act of flying toward a flying honey bee from an ambush position; (b) Beecatcher: the act of flying toward a flying honey bee from an ambush position and immediately returning to the same ambush position; (c) Chase: the act of chasing a flying honey bee; (d) Parasitization: the act of chasing a flying honeybee followed by contact. Red arrows indicate the flight directions of S. tricuspis. Blue arrows indicate the flight directions of A. mellifera. (Drawings from [7]).

Figure 3

Number of aggressions of S. tricuspis toward honey bees detected during the four days (19–22 August) of direct observations, from 8:00 to 19:00, in Pisa province, Italy.

Figure 4

Number of aggressions of S. tricuspis toward flying-out honey bees (black histograms) and flying-in honey bees (gray histograms) during the four days (19–22 August) of direct observations, from 8:00 to 19:00, in Pisa province, Italy.