Life History and Description of Immature Stages of Aciurina Thoracica (Diptera: Tephritidae) on Baccharis Sarothroides in Southern California
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ARTHROPOD BIOLOGY Life History and Description of Immature Stages of Aciurina thoracica (Diptera: Tephritidae) on Baccharis sarothroides in Southern California DAVID H. HEADRICK AND RICHARD D. GOEDEN Department of Entomology, University of California, Riverside, CA 92521 Ann. Entomol. Soc. Am. 86(1): 68-79 (1993) ABSTRACT Aciurina thoracica Curran forms galls on branches of at least three species of Baccharis in southern California. The egg, second and third instars, and puparium obtained from B. sarothroides Gray are described and illustrated. Aciurina thoracica's median oral lobe is described and illustrated. The egg is inserted singly into branch tips of B. sarothroides in early spring. Gall and larval growth continue through summer and fall, and pupariation occurs in early winter. Adults emerge in late winter or early spring, mate, and oviposit into newly forming branch tips. Adult behavior including courtship and copulation is described and compared with other Aciurina species. Principal hymenopter ous natural enemies of A. thoracica include two solitary, primary endoparasitoids, Dinar mus sp. (Pteromalidae) and Eurytoma sp. (Eurytomidae); two solitary primary ectopara sitoids, Pteromalus sp. and Mesopolobus sp. (Pteromalidae); and Eupelmus spp. (Eupelmidae) reared as solitary, primary endo- and ectoparasitoids. KEY WORDS biology, galls, mating behavior THIS STUDY is derived from field studies begun more difficult to study in the field during each of in 1989 on the tephritid associates of Baccharis 2 successive yr. sarothroides Gray in southern California, and it We collected galls and adults on B. sarothro continues a series of life-history studies on non- ides at Otay Mesa, Chariot Canyon, and 5 km frugivorous tephritids associated with Aster- south of Alpine, all in southern San Diego aceae in southern California. Much of what was County. The Otay Mesa site overlooks San known about the genus Aciurina was strictly tax- Ysidro just north of Tijuana, Mexico, at 45 m onomic before Tauber & Tauber (1967) con- elevation. The Alpine site is inland northeast- ducted their study of the biology of Aciurina ward at 480 m elevation. Collections in Chariot ferruginea (Doane). Wangberg (1981) described Canyon south of Banner were made at 1,050 m the biologies and galls of eight species of Aci- elevation. urina on Chrysothamnus spp. in Idaho. The Field data were supplemented by laboratory most extensive studies to date on the biologies cagings of swept or reared single males and fe of Aciurina were conducted in New Mexico on males or paired reared adults of opposite sex. A. trixa Curran (Dodson & George 1986, Dodson The adults were reared from larvae and puparia 1987). Both studies treated host plant associa- dissected from galls held separately in cotton tions, reproductive behavior, and morphology; stoppered, glass shell vials within humidity the former study also discussed taxonomy. Jen- chambers at 22-24°C and 76% RH. Adults were kins (1990) described the reproductive behavior subsequently held in 850-ml, clear plastic cages of A. mexicana (Aczel) in Arizona. fitted with screened lids for ventilation and basal This article reports field and laboratory data on water reservoirs. Absorbent cotton wicks and the immature stages, hosts, biology, mating be- bouquets of excised vegetative branches of B. havior, and natural enemies of A. thoracica Cur- sarothroides passed through a hole in each cage ran. bottom. Honey striped with a bulb and syringe on the underside of the lids provided food for the flies. Materials and Methods Mating trials employed disposable plastic Our field studies of the biology of A. thoracica 10-cm petri dish arenas in the manner of Jenkins began in 1989 during the second year of a severe (1990), modified by the inclusion of a flattened, drought in southern California. Consequently, water-moistened pad of absorbent cotton spotted flies became progressively less common and with honey. The 1-h trials were run at room tem 0013-8746/93/0068-0079$02.00/0 © 1993 Entomological Society of America January 1993 HEADRICK & GOEDEN: LIFE HISTORY OF Aciurina ihoracica 69 perature under artificial lighting between 1100 and 1500 hours PST, when males readily dis- played courtship behavior; however, during the 1.5-d trials, copulation was observed only after 1400 hours, and usually at dusk under natural lighting. Immature stages were described using scan- ning electron microscopy (SEM) from five eggs dissected from gravid females as well as five each of second and third instars and two puparia dissected from branch tip galls on B. sarothro- ides. All stages were fixed in 70% EtOH, later rehydrated to distilled water, and osmicated for 24 h. Specimens were then dehydrated to 100% EtOH in a graded series of acidulated EtOH, critically point dried, mounted on stubs, and sputter coated for SEM (Headrick & Goeden 1990,1991). Micrographs were prepared at 15 kV accelerating voltage with Polaroid 55 P/N film on a JEOL JSM-C35 SEM, located in the Depart- ment of Nematology, University of California, Riverside. Eggs, second and third instars, and puparia are described using the format and no- menclature adopted by Headrick & Goeden (1990), as modified by Headrick & Goeden (1991). Description of the second instar is limited to observed differences from the third instar. The mouthparts of three third instars of A. tho- racica were dissected in 70% EtOH to which 1% alcoholic acid fuchsin was added as a visual aid. Larvae were obtained from the immature Tephritidae research collection of D.H.H. No- Fig. 1. Egg of A. thoracica: (A) habitus, dissected menclature for the cephalopharyngeal skeleton from gravid female; (B) detail of pedicel. follows that of Teskey (1981). Plant names follow Boldt (1989); Aciurina names follow Steyskal 0.05 ± 0.002 mm long, 0.08 ± 0.002 mm wide (1984) or Dodson & George (1986). (Fig. IB); polygonal reticulations arise around Voucher specimens of A. ihoracica from each middle of egg body, farther down one side than study site are located in the research collection opposite side; posterior end smooth, rounded, of R.D.G. (Department of Entomology, Univer- fragile. sity of California, Riverside); voucher specimens The posterior end is embedded in host plant of parasitoids are in a separate collection of tissue at oviposition at an angle, such that the reared hymenopterous parasitoids of California exposed side of the egg opposite the branch Tephritidae belonging to R.D.G. Means ± SEM bears reticulations farther along the egg body are provided throughout the paper. than the side nearest the branch (Fig. 1A). The eggs of A. thoracica are similar in size and shape to those oiTephritis baccharis (Coquillett) (Goe- Results and Discussion den & Headrick 1991a) and other Tephritis spp. Taxonomy. Aciurina ihoracica was described (Jenkins & Turner 1989). Noteworthy differences from a single female collected from San Diego in the egg chorion of A. thoracica from that of County, CA (Curran 1932). It belongs to the T. baccharis are no distinct pores circumscribing Aplopappi group as defined by Steyskal (1984), the pedicel, deeper reticulations, papillate struc- which also contains A. aplopappi (Coquillett) tures at the polygonal junctions, and a verrucate and A. mexicana. This group is characterized by surface. The ova of A. thoracica also differ mark- a similar habitus and wing venation as well as edly from eggs of A. ferruginea illustrated by several distinguishing features of the ovipositor Tauber & Tauber (1967), which have elongate (Steyskal 1984). pedicels. Our dissections of swept, gravid fe- Egg. Ova white, fusiform; 25 averaged 0.87 ± males of A. ferruginea confirmed this finding. 0.01 mm long (range, 0.78-0.92 mm), 0.31 ± 0.01 The ova of A. ferruginea are similar in size and mm wide (range, 0.26-0.37 mm) (Fig. 1A); ante- shape to those ofParacantha gentilis Hering, but rior half bears distinct polygonal reticulations on are not stored in the ovaries as illustrated for the chorion increasing in height near anterior pole; latter species (Headrick & Goeden 1990; unpub- anterior end tapers to honey-combed pedicel, lished data). It is unclear why A. ferruginea has 70 ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA Vol. 86, no. 1 an egg with a long pedicel and A. thoracica does 1), a median scar (Fig. 2H, 2), four interspiracular not. Paracantha cultaris (Coquillett), like P. gen processes (Fig. 2H, 3); caudal sensilla around tilis, has eggs with elongate pedicels (Cavender margin of caudal segement in four-dorsal, six- & Goeden 1984). ventral arrangement; sensilla consist of cuticular Third Instar. Third instar creamy white, rings, with smaller papilla centrally each bearing oblong-elliptical, dorsally rounded, ventrally open pores. flattened; superficially smooth; lacks distinct In larvae of Neaspilota viridescens Quisen segmental depressions; (Fig. 2A); mouth hooks berry, the median oral lobe was reported to be tridentate; teeth stout, sharply curved ventrad attached basally to the labial lobe (Goeden & (Fig. 2B, 1; Fig. 3); median oral lobe laterally Headrick 1991c); however, we reported that lar compressed, tapers anteriad between mouth vae were not observed feeding, and thus we hooks; paired, thin, darkly pigmented flanges could not ascertain the independent movement project ventrad from darkly pigmented dorsal of the median oral lobe, as first noted with larvae ribs supporting ventral lobe (Fig. 2B, 2; Fig. 3 A of Paracantha gentilis, whose median oral lobe and B); ventral lobe of median oral lobe smooth, is free basally of the labial lobe (Headrick & attached basally to labial lobe (Fig. 3A); labial Goeden 1990). Our observations of A. thoracica lobe divides anterioventral margin of gnatho larvae lead us to conclude that the median oral cephalon, muscles insert on ventral margin; la lobe is independently movable whether it is at bial lobe bears two pore sensilla anteriorly (Fig. tached basally to the labial lobe or not. The en 2B, 3; best seen in Fig. 4D, 2); labial sclerite tire structure consisting of the median oral lobe quadrangular, medially divided, darkly pig and the labial sclerite moves up and down.