The tachinid parasitoid Zelia tricolor (Coquillett) has a wide distribution in North America, ranging from Nevada to Pennsylvania, and south to Mexico and Florida (O'Hara & Wood 2004). Coquillett (1899) did not specify a host association when describing the species. Palmer & Tomley (1993) reported Amniscus perplexus Haldeman (= Astylopsis perplexa (Haldeman)) from Baccharis halimifolia L. (Asteraceae) as a host of “Metadexia near tricolor Coquillett”; a specimen from that study in the National Museum of Natural History, Smithsonian Institution (USNM) confirms that the tachinid is Zelia tricolor. Tindall & Fothergill (2010) list Rhodobaenus sp. from Dahlia sp. stems (citing Wray 1950) and Dectes texanus LeConte from soybean (Glycine max (L.) Merr.) as Z. tricolor hosts. To this list we add the following: Rhodobaenus quinquepunctatus (Say) from Bidens cernua L. (Asteraceae), Hippopsis lemniscata (F.) from Ambrosia artemisiifolia L. (Asteraceae), Oberea tripunctata (Swederus) from an unknown plant, and Languria bicolor (F.) from “Cacalia” sp. (Asteraceae; species now included in several genera) (Table 1).
Rhodobaenus quinquepunctatus is a stem boring, univoltine, Curculionidae known from central and eastern North America from Mexico to Canada that overwinters as an adult (Vaurie 1981). The Rhodobaenus species noted by Wray (1950) was R. quinquepunctatus as it is the only member of the genus found in North Carolina that feeds on Dahlia (Vaurie 1981). An additional specimen of Z. tricolor found in the USNM from ILLINOIS: Urbana, Aug 26, 1949, is labeled “parasite of Rhodobaenus tridecempunctatus pulchellus in stem of Bidens cernua.” Vaurie (1981) noted that R. tridecempunctatus var. pulchellus (Gyllenhal) of Blatchley & Leng (1916) actually is R. quinquepunctatus, and true R. pulchellus does not occur north of Mexico. Thus, this record refers to R. quinquepunctatus.
Hippopsis lemniscata is a univoltine cerambycid that primarily utilizes A. artemisiifolia as a larval food plant, overwintering as a larva within the stem (Piper 1977; Lingafelter 2007). It is commonly found in the central and southern United States (Lingafelter 2007). Seven Z. tricolor adults were reared from 12 H. lemniscata larvae harvested from common ragweed stems collected in Pemiscot County, Missouri on 8 Mar 2010, placed on artificial diet (Product #F9703B, Bio-Serv, Frenchtown, NJ) and held in a rearing room at 16:8, 25°C from 9 Mar 2010 to adult emergence. Six Z. tricolor were noted as pupae outside their hosts on 3 Apr 2010 and eclosed as adults between 9 Apr 2010 and 11 Apr 2010; the seventh Z. tricolor was noted to have pupated outside its host on 9 Apr 2010 and eclosed on 24 Apr 2010. We identified H. lemniscata larvae by using Craighead (1923) and by rearing of non-parasitized larvae to adults for identification with Lingafelter (2007). These specimens are housed in the USNM collection.
Oberea tripunctata (Swederus) is a wood boring cerambycid that takes 2 years to complete development to adult in Minnesota (Ruggles 1915). It is widespread in eastern and central North America and larvae bore in living branches of trees and shrubs from many plant families (Lingafelter 2007). A USNM specimen of Zelia tricolor from PENNSYLVANIA: Harrisburg, was reared from O. tripunctata; no other data were provided on the label.
Languria bicolor is a stem boring languriid and is widespread in eastern and central North America (Vaurie 1948). Although Vaurie (1948) suggests that L. bicolor overwinters in the adult stage, they may be plastic in regard to overwintering lifestage as is the congener L. mozardi Latreille (Wildermuth & Gates 1920). A specimen of Z. tricolor in USNM from MARYLAND: Cabin John Bridge, iss[ued; i.e., eclosed] 5 Sep 1904 also bears a label: “Par: on Languria bicolor in Cacalia”.
Tachinid species are koinobiont endo-parasitoids and typically kill their hosts when completing their development (Stireman et al. 2006). Dissection or rearing of host larvae is the only reliable means of detecting these parasitoids; therefore, elucidating the parasite-host relationship is difficult. Data presented are opportunistic and provide documentation of host-parasite relationships.
Limited data reveal aspects of Z. tricolor biology: (1) all known Z. tricolor hosts are stem boring beetle larvae; (2) these larvae may or may not be univoltine; (3) Z. tricolor can overwinter as larvae within host larvae; (4) Z. tricolor is able to find hosts in 2 families of living herbaceous plants and also has the ability to locate hosts (e.g., Oberea tripunctata) in a living woody plant; (5) Z. tricolor has a 5 (Tindall & Fothergill 2010) to 15-d pupal time under lab conditions after overwintering in host Cerambycidae; and (6) there was a 58% parasitism rate within H. lemniscata, demonstrating that Z. tricolor may have a significant impact on H. lemniscata populations (and vice versa). Additional efforts are needed to document other hosts for Z. tricolor and to determine its ecological role in shaping stem boring beetle populations.
INSECTS UTILIZED AS LARVAL HOSTS BY ZELIA TRICOLOR AND THE PLANTS IN WHICH THEY WERE FOUND.
New host records are given for Zelia tricolor (Coquillett), a tachinid fly that is a parasitoid of stem-boring beetles. New host records are Cerambycidae: Hippopsis lemniscata (F.) and Oberea tripunctata (Swederus); Curculionidae: Rhodobaenus quinquepunctatus (Say); and Languriidae: Languria bicolor (F.). The few previously reported hosts of Z. tricolor are summarized.