Parasite Lost: Chemical and Visual Cues Used by Pseudacteon in Search of Azteca instabilis

Journal of Insect Behavior, May 2011

An undescribed species of phorid fly (genus: Pseudacteon) parasitizes the ant Azteca instabilis F Smith, by first locating these ants through the use of both chemical and visual cues. Experiments were performed in Chiapas, Mexico to examine a) the anatomical source of phorid attractants, b) the specific chemicals produced that attract phorids, and c) the nature of the visual cues used by phorids to locate the ants. We determined that phorid-attracting chemicals were present within the dorsal section of the abdomen, the location of the pygidial gland. Further experiments indicate that a pygidial gland compound, 1-acetyl-2-methylcyclopentane, is at least partially responsible for attracting phorid flies to their host. Finally, although visual cues such as movement were important for host location, size and color of objects did not influence the frequency with which phorids attacked moving targets.

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Parasite Lost: Chemical and Visual Cues Used by Pseudacteon in Search of Azteca instabilis

Kaitlyn A. Mathis 0 1 Stacy M. Philpott 0 1 Rayane F. Moreira 0 1 0 R. F. Moreira Department of Natural Science, Hampshire College , 893 West St., Amherst, MA 01002, USA 1 S. M. Philpott Department of Environmental Sciences, University of Toledo , 2801 W. Bancroft Street, Toledo, OH 43606, USA 2 ) University of California , Berkeley , 137 Mulford Hall, Berkeley, CA 94720, USA An undescribed species of phorid fly (genus: Pseudacteon) parasitizes the ant Azteca instabilis F Smith, by first locating these ants through the use of both chemical and visual cues. Experiments were performed in Chiapas, Mexico to examine a) the anatomical source of phorid attractants, b) the specific chemicals produced that attract phorids, and c) the nature of the visual cues used by phorids to locate the ants. We determined that phorid-attracting chemicals were present within the dorsal section of the abdomen, the location of the pygidial gland. Further experiments indicate that a pygidial gland compound, 1-acetyl-2-methylcyclopentane, is at least partially responsible for attracting phorid flies to their host. Finally, although visual cues such as movement were important for host location, size and color of objects did not influence the frequency with which phorids attacked moving targets. - Parasitoids have evolved effective and efficient methods of host location, many of which involve utilization of chemical and visual cues. Social insects, such as ants, use chemical communication as a primary form of interaction along with some visual and tactile signals (Jackson and Morgan 1993; Hlldobler 1999). The chemical signals exchanged between ants are often complex and species specific (Jackson and Morgan 1993). The reliability of these intraspecific chemical signals thus makes them effective host location cues for ant parasitoids such as phorid flies (Brown and Feener 1991; Feener et al. 1996; Morehead and Feener 2000). Many dipteran parasitoids in the family Phoridae use ants as hosts (Disney 1994). These phorid species are commonly referred to as the decapitating flies. In Pseudacteon species phorid flies that attack Solenopsis, the adult flies hover over ant hosts and dive down to oviposit an egg beneath the ants exoskeleton. The larva hatches and moves through the ant into the head where it eats the contents and uses the empty shell as a case in which to pupate, eventually causing the ants head to fall off (Cnsoli et al. 2001). Later, the adult phorid fly will emerge from the head of the dead ant to begin the cycle again (Porter 1998; Disney 1994). Although phorids have direct parasitic effects on ants (i.e. cause ant mortality), they also significantly change ant foraging behavior by limiting host resource acquisition behavior, modifying ant competitive hierarchies, and dampening ant effects on herbivores (Feener 1981; Feener and Brown 1992; Orr et al. 1995; Vandermeer et al. 2002; Philpott 2005b). A number of different phorid-ant relationships have been described and, for each, it is generally reported that phorids use chemical and visual cues to locate ant hosts, but the specific cues used by phorid species to locate particular ants differ (Feener et al. 1996; Morehead and Feener 2000; Vander Meer and Porter 2002; Chen et al. 2009; Maschwitz et al. 2008; Gazal et al. 2009). Ants produce a range of pheromones with different functions in different glands throughout their bodies. These pheromones are responsible for behaviors such as trail marking, worker recruitment, and alarm signaling, each of which has been linked to attracting phorids. For example, the phorid parasitoid, Apocephalus paraponerae Borgmeier, is attracted to 4-methyl-3-heptanone and 4-methyl-3-heptanol produced in the mandibular glands of its host, Paraponera clavata Fabricius (Feener et al. 1996). The thoraces of ants contain the metaplural glands, which are the source of the kairomone known to attract Pseudacteon tricuspis Borgmeier to Solenopsis invicta Buren (Chen and Fadamiro 2007). The abdomens of ants also contain several glands that produce pheromones, although to our knowledge no compounds present within abdominal glands have previously been reported as phorid attractants. The small amount of information reported on visual cues used by phorid flies indicates that these cues can also vary based on individual phorid-ant relationships. Some phorids oviposit on stationary hosts, whereas others require host motion (Wuellner et al. 2002). Other phorids select hosts based on host size or color (Owens and Prokopy 1986). For example, Apocephalus paraponerae attack stationary individuals preferring hosts with large body size (Moorehead and Feener 2000). Neodohrniphora curvinervis Malloch, a parasitoid of Atta cephalotes Linnaeus, also prefer larger worker castes as hosts (Orr 1992). Preference for larger hosts also occurs in Pseudacteon crawfordi Coquillett, a parasitoid of fire ants (however based on range phorid species might be Pseudacteon hippeus Plowe (...truncated)


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Kaitlyn A. Mathis, Stacy M. Philpott, Rayane F. Moreira. Parasite Lost: Chemical and Visual Cues Used by Pseudacteon in Search of Azteca instabilis, Journal of Insect Behavior, 2011, pp. 186-199, Volume 24, Issue 3, DOI: 10.1007/s10905-010-9247-3