Into the mouth of the dragon: Systematics and biology of a specialized ant parasitoid
Judith Herreid
University of California, Riverside - Entomology Department, Riverside, CA 92507
The genus Orasema (Eucharitidae: Oraseminae) is a group of specialized immature ant parasitoids. The eggs are oviposited into plant tissue. The planidial 1st instar larva must then gain access to the ant brood through specialized behaviors. Orasema has biological control potential against the invasive fire ant (Solenopsis) and little fire ant (Wasmannia). I am completing a revision of a species group from the new world clade from the southwestern United States and into Mexico. My revision will include both behavioral information and morphological and molecular techniques that will provide insights into phylogenetic relationships within Orasema. It will also allow inferences about local confined radiations. The Orasema simulatrix species group is potentially monophyletic and members of the group exhibit unique associations with extrafloral nectaries (EFN) on Chilopsis linearis (Bignoniaceae). Pheidole, one of the known ant hosts of the species group, feeds on the EFNs. The planidia are often found inside EFNs. This association may facilitate access to the host’s brood by allowing the planidia to attach or be ingested into the host ant mouth parts. Although Pheidole is the only recorded host of the Orasema simulatrix species group, both Formica and Camponotus have been found with planidia from desert willow in their mouthparts. This means accidental host associations may be happening in this group. My fieldwork in southern Arizona has begun expanding behavioral knowledge of Orasema by making accurate plant host associations and determining how planidia are using their EFN associations to access the ant brood. Continued work on Orasema behaviors could lead to the use of this genus as a biological control agent.
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