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Home , Anagrus armatus, Brown planthopper, Delphacidae, Delphacodes, Elenchidae, Laodelphax

SYSTEMATICS Description, Life History, and Parasitism of a New of Delphacid (: Fulgoroidea)

1 2 JAMES T. CRONIN AND STEPHEN W. WILSON

Ann. Entomol. Soc. Am. 100(5): 640Ð648 (2007) ABSTRACT scolochloa Cronin & Wilson (Hemiptera: Fulgoroidea) is a newly discov- ered delphacid planthopper that feeds and oviposits exclusively on the stems of sprangletop, Scolochloa festucacea (Willd.) Link (: Pooidae), in the prairie pothole region of northeastern North Dakota. D. scolochloa is bivoltine. It is also wing dimorphic, but populations are composed predom- inantly of ßightless brachypters. Macropters incur a substantial cost in terms of reduced longevity and fecundity relative to brachypters. The parasitoid complex attacking D. scolochloa consists of two egg parasitoids, nigriventris Girault and Anagrus columbi Perkins (: Mymaridae), and one undescribed dryinid. The proportion of eggs parasitized averages 21%, and egg parasitization is density independent.

KEY WORDS Anagrus nigriventris, egg parasitoid, planthopper, prairie potholes, Scolochloa festucacea

Grass-feeding delphacids have been the subject of ex- L. (Kiritani 1979, Wilson and Claridge 1985). These tensive ecological research, primarily because several delphacids also serve as hosts to mymarid, strep- species are vectors of pathogens of economically impor- sipteran, and dryinid parasitoids, an assemblage of tant grasses (Wilson 2005). In North American grass- parasitoids very comparable to that found for many lands and salt marshes, researchers have focused on fau- planthopper pest species (e.g., Oˆ take 1970, Bentur et nal surveys (e.g., Hendrickson, 1930, Wilson et al. 1993, al. 1982, Fowler et al. 1991). The study of hostÐpara- Hamilton 2002), systematics and morphology (e.g., Wil- sitoid interactions in species of grassland delphacids son 1982, Miller and Wilson 1999), life histories (e.g., may provide insight or potential biocontrol agents for Holder and Wilson 1992), and mating behavior (e.g., the suppression of related pest species. Heady and Denno 1991, Heady and Wilson 1990). Del- Here, we describe a new species of delphacid pl- phacids also have been used to address a broad range of anthopper and provide data on its biology, host range, ecological questions regarding plantÐherbivore interac- rate of macroptery, and population dynamics. We also tions (e.g., Tallamy and Denno 1979, Denno 1983, Denno identify the parasitoid species that attack the plan- et al. 1986, Wilson et al. 1994), life history theory (e.g., thopper, quantify rates of parasitism, and test whether Denno and Dingle 1981, Denno and McCloud 1985, the proportion parasitized among host patches Huberty and Denno 2006), population dynamics (e.g., depends on host density. Denno 1983, Strong 1989, Reeve et al. 1994), interspeciÞc competition (Denno and Roderick 1992, Denno et al. Materials and Methods 2000, Ferrenberg and Denno 2003), predatorÐprey in- teractions (Do¨bel and Denno 1994, Cronin et al. 2004, Study Location and Host Plant. Collection of spec- Fagan and Denno 2004), hostÐparasitoid interactions imens and census of planthopper and parasitoid pop- (e.g., Stiling and Strong 1982; Cronin and Strong 1990, ulations occurred in the prairie pothole region of 1993, 1999; Cronin 2003b), food web structure (e.g., northeastern North Dakota (Petersburg, Nelson Denno et al. 2002, Finke and Denno 2003, Gratton and County; 48.02097Њ N, 98.12230Њ W). This formerly gla- Denno 2003), dispersal and metapopulation dynamics ciated area is characterized by numerous seasonal and (Cronin 2003a, Haynes and Cronin 2006), and landscape permanent ponds (van der Valk 1989), and it is an ecology (Haynes and Cronin 2003, 2006; Cronin and important breeding habitat for waterfowl (Batt et al. Haynes 2004). 1989). Among the wetland bordering these Some grass-feeding delphacids are ecologically sim- ponds is the native sprangletop or common river grass, ilar to pests such as the , Nilapar- Scolochloa festucacea (Willd.) Link (Poaceae: Pooi- vata lugens (Stål.), a serious pest of , Oryza sativa dae). Sprangletop is circumpolar in distribution and in North America ranges from northern Iowa and Ne- 1 Corresponding author: Department of Biological Sciences, braska to southcentral Canada and west to Oregon Louisiana State University, Baton Rouge, LA 70803 (e-mail: (Gould 1968, Clayton and Renvoize 1986). Ecologi- [email protected]). 2 Department of Biology, University of Central Missouri, Warrens- cally, it is an emergent hydrophyte, and it is found burg, MO 64093. where water levels ßuctuate from 0 to 150 cm above

0013-8746/07/0640Ð0648$04.00/0 ᭧ 2007 Entomological Society of America September 2007 CRONIN AND WILSON:BIOLOGY OF NEW SPECIES OF DELPHACID PLANTHOPPER 641

Fig. 1. D. scolochloa. (A) Adult brachypterous female with dryinid parasitoid sac. (B) Macropterous and brachypterous females. (C) Egg clusters on S. festucacea stems that have by parasitized by Anagrus spp. (plant epidermis has been removed to expose eggs in the upper egg cluster). the soil surface (Sculthorpe 1967). Sprangletop often Planthopper . The specimens collected forms pure stands several meters deep along the pond from S. festucacea represent a new species, and they margins and as small clonal patches further in open are described below. Descriptions are based on nine shallow water (Smith 1973; J.T.C., unpublished data). males and 34 females. Using an ocular micrometer, Population Census. Three semipermanent ponds, body length was measured from the apex of the vertex broadly bordered by sprangletop, were used in this to posterior aspect of the abdomen. Thoracic length study (Ponds 100, 109, and N29-1). The ponds were was measured along the midline from the anterior 1Ð3 ha in size and were separated from each other by aspect of the pronotum to the posterior aspect of the 1.8Ð5.6 km. Shortly after spring thaw, mid-May 1998, mesonotal scutellum as the metanotum is obscured by the sprangletop bordering each pond was sampled the forewings. To describe and illustrate the male and with a sweepnet. Three sets of 10 sweeps each were female genitalia, the abdomen was removed and conducted per pond. Sweep samples were transported placed in a 10% KOH solution overnight, then washed on ice to the laboratory, and were in- in distilled water; genitalia were stored in genitalia spected to determine stage (nymph or adult), sex, capsules Þlled with glycerol (Wilson 2005). The ter- wing morph (brachypters versus macropters; Fig. 1, A minology used in describing the female genitalia fol- and B), and presence of parasitoids protruding from lows Heady and Wilson (1990). between the abdominal segments (dryinid larval sac Host Range of D. scolochloa. To ascertain the host or strepsipteran cephalothorax) (Fig. 1A). Surveys range of the planthopper, we caged planthopper adults were conducted at 2-wk intervals until the end of the onto potted stems of the 11 dominant plant species at our summer when sprangletop had completely senesced Þeld sites. These plant species were the grasses spangle- (early September). The survey was continued each top, switch grass (Panicum virgatum L.), prairie season for 3 yr. cordgrass (Spartina pectinata Link), and smooth brome For each planthopper generation, after adults had (Bromus inermis Leyss.); common reed [Phragmites aus- become scarce, we conducted a census of planthopper tralis (Cav.) Trin]; sedges (Carex sp.); rushes (Scirpus eggs. Twenty-Þve sprangletop stems with planthopper sp.); cattails (Typha spp.); Canada goldenrod (Solidago eggs were haphazardly collected from each pond. canadensis L.); smart weed (Polygonum sp.); and thistle Stems were left to incubate for3datroom temper- (Circium sp.). Two common grass crops, corn (Zea mays ature (stem bases were submerged in water) to ensure L.) and wheat (Triticum aestivum L.), also were included that recently parasitized hosts could be identiÞed. in this study. Young, nonßowering shoots of the noncrop Stems were subsequently dissected under a stereo- plants were excavated from the Þeld in early June 1999 scopic dissecting microscope (10ϫ) to expose plan- and potted in Pro-mix BX soil (20-cm-diameter pots). thopper eggs inserted just beneath the stem epidermis Corn was grown from seed (Burpee Seed Co., Warm- (Fig. 1C). Planthopper eggs were identiÞed as either inster, PA, Early Choice Hybrid SE variety), and wheat healthy (developing white embryos or as cast chori- was obtained as seedlings from a local farmer. Both crop ons, indicating successful emergence), parasitized plants were grown in 20-cm pots by using Pro-Mix BX. (red immatures, or host chorions with circular exit Clear Mylar sheeting, formed into tubes, were inserted holes, indicating successful emergence), or dead over the plants. The tops of the cages were constructed (deßated or brown eggs). A subset of planthopper of mosquito netting hot-glued to the Mylar. Twenty-Þve nymphs and adults and egg parasitoids were preserved recently eclosed adult planthoppers were added to each in 70% ethanol for later identiÞcation of species. cage, and there were three caged plants per plant spe- 642 ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA Vol. 100, no. 5 cies. Cages were inspected daily for live planthoppers and evidence of feeding (excretion of ). After all planthoppers had died, the plants were carefully in- spected for planthopper eggs. Longevity and Fecundity of Wing-Dimorphic Fe- males. Several hundred late instars of D. scolochloa, collected from the Þeld in late May 1998, were placed on potted sprangletop plants that were enclosed with a Mylar cage (see above). Each day, newly eclosed adults were removed and sorted by sex and wing type. Adults were quickly transferred to stem cages in groups of either six brachypterous or six macropterous females. In addition, two macropterous males were added to each cage (Ͼ99% of males are macropterous in this species). The stem cage was constructed of a 10-cm-long by 2.5-cm-diameter acetate tube. High- density foam sealed the ends of the tube around the stem and kept the stem positioned in the center of the tube. The experiment consisted of 10 replicate cages per wing type. Every day until all planthoppers had died, the cages were inspected, and the number of live females was counted. Planthoppers were gently aspirated and transferred to new stem cages at 2-day intervals. This Fig. 2. D. scolochloa male external genitalia. (A) Py- procedure ensured that planthoppers had high-quality gofer, anal tube, aedeagus, and style, left lateral view. (B) host material for feeding and oviposition. Also, males Styles, caudal view. (C) Anal tube, right lateral view. (D) were maintained at two individuals per cage through- Anal tube, caudal view. (E) Aedeagus, right lateral view. out the experiment to ensure that females were not (F) Aedeagus, left lateral view. sperm limited. Differences in survival curves between female 0.60 Ϯ 0.022 mm, female 0.70 Ϯ 0.057 mm; n ϭ 7 males, brachypters and macropters were analyzed with a 32 females. WilcoxonÕs rank test (Pyke and Thompson 1986). We Body pale, yellow/light brown to dark brown with also tested for differences in median and maximum life fuscous markings. Vertex subquadrate with prominent spans (days to 50 and 100% mortality per replicate, darker lateral carina, concolorous V-shaped posteri- respectively) and fecundity by using two-sample t- orly directed carina near middle; in lateral view, vertex tests. We used two fecundity metrics, mean daily fe- curving onto frons. Frons narrow, approximately cundity (ϭtotal eggs laid/summation of females alive twice as long as wide, bordered by darker subparallel to start each day) and mean lifetime fecundity (ϭtotal lateral carinae, with concolorous weak median longi- eggs laid/initial number of females) per replicate tudinal carina. Clypeus with prominent partial median cage. All tests were performed in SYSTAT 11 (Systat longitudinal carina. Antennal scape subcylindrical, Software, Inc., Point Richmond, CA). pedicel length Ϸ2.5ϫ that of scape. Parasitism and Host Density. Based on stem collec- Pronotum with lateral carinae curving posterolat- tions made during the census, we examined the relation- erally, paralleling curvature of compound eyes; with ship between host density and proportion parasitized prominent median longitudinal carina. Mesonotum among stems. Spatial density dependence was examined length about twice that of pronotum; with straight, using separate least-squares regression models for each posterolaterally directed lateral carinae and a median site (n ϭ 3) and planthopper generation (n ϭ 6) for a longitudinal carina. Forewings translucent pale total of 18 tests. Eggs per stem was ln transformed, and brown, veins concolorous bearing short setae; mac- proportion parasitized was arcsine square root trans- ropters with forewing narrow, broadly rounded api- formed to achieve normality and homogeneity of vari- cally and extending well beyond apex of abdomen; ances (Sokal and Rohlf 1995). We report the fraction of brachypters with forewing subquadrate extending to tests that had a positive or negative slope and how many abdominal tergite 6. Legs with apices of tarsi fuscous; were statistically signiÞcant (P Ͻ 0.05). metatibial spur subequal in length to that of basal metatarsomere, with row of very small black tipped teeth on posterolateral aspect; basal metatarosmere Results Ϸ3ϫ length of middle metatarsomere, which is sub- equal in length to that of terminal metatarsomere. Abdominal tergite 3 fuscous. Delphacodes scolochloa Cronin & Wilson, Male genitalia (Fig. 2). Pygofer pale brown with New Species black marking on ventrocaudal aspect; in lateral view, Salient Features. Total length: male 1.92 Ϯ 0.095 subquadrate, with caudal margin in dorsal one third mm, female 3.04 Ϯ 0.227 mm; thoracic length: male gently concave; diaphragm armature shining black, September 2007 CRONIN AND WILSON:BIOLOGY OF NEW SPECIES OF DELPHACID PLANTHOPPER 643

Fig. 4. Mean Ϯ SE number of adult D. scolochloa (sum of three sets of sweeps) among three prairie potholes based on biweekly samples for 3 yr (1998Ð2000).

Snow Museum, University of Kansas). PARATYPES: 8 males, 33 females, same data (2 males, 4 females de- posited in the Snow Museum, the remainder deposited in SWW Collection). Distribution. This species is known from S. festu- cacea from eastern North Dakota, but it is likely to be more widely distributed in North America because its host plant is found along the margins of lakes and prairie potholes from central Canada south to Iowa and west to Oregon. Etymology. D. scolochloa is named for the of its host plant. Life History. D. scolochloa overwinters as mid-instar nymphs concealed beneath the senescent leaf sheaths that are loosely attached to the sprangletop stems. In Fig. 3. D. scolochloa female external genitalia. (A) Apical early May, corresponding with the emergence of new portion of abdomen, ventral view. (B) Apical portion of abdomen, left lateral view. sprangletop shoots, the nymphs emerge from their winter refuge and begin to feed. Planthoppers extract phloem from the stems, typically feeding above the extending posteriorly as a bulbous process. Anal tube, water line but below the lowest unfurled leaf. How- in lateral view, with a pair of broadly separated, ever, on occasion, some feeding does take place at the curved, ventroanteriorly directed spinose processes base and abaxial surface of leaves. Toward the end of originating on the ventrocaudal aspect of the tube. May, adults achieve maximal density (Fig. 4). Females Styles, fuscous; in caudal view, curved dorsolaterally at lay eggs in clusters just beneath the stem epidermis base then elongate, subparallel narrowing abruptly to (Fig. 1C) and in complete overlap with their feeding a small pointed apex. Aedeagus subcylindrical, apex sites. Emergence of nymphs follows egg laying by Ϸ2 broadly rounded, gonopore on ventral aspect near wk. Planthoppers have two nonoverlapping genera- apex; with curving row of Ϸ20 teeth extending from tions per summer; peak adult densities for the second dorsal aspect anterolaterally on left side to near generation occur in the middle of July (Fig. 4). By the middle. latter half of August, no adults are present in the Female genitalia (Fig. 3). Tergite 9, in ventral view, population. elongate, each side broad with length Ϸ3ϫ width, Feeding and oviposition on the stems of sprangletop apex rounded. Anal tube subcylindrical. Valvifers of caused necrotic lesions to form and be visible within segment 8 each covering tergite 9 anterolaterally; 2 wk. The damage was especially evident after the elongate, slender, broadly convex on lateral aspect, outbreak of planthoppers in July 1998 (Fig. 4). How- sinuate on median aspect. Lateral gonapophyses of ever, heavy stem damage at this time did not translate segment 9 elongate, spatulate posteriorly. In lateral into a reduction in plant height or ßowering frequency view, median gonapophyses of segment 9 saber- at the end of the growing season. Based on a sample shaped, with Ϸ30 prominent small teeth on dorsal of 100 heavily scarred and 100 unscarred stems at site margin in distal one half. Gonapophyses of segment 8 100, heights differed by only 3% (scarred, 1.22 Ϯ Ϯ ϭ ϭ adhering tightly to median gonopophyses of segment 0.04 m and unscarred, 1.26 0.05 m; t198 0.62, P 9; slender, acute apically. 0.27). Flowering rates were actually slightly higher for Types. HOLOTYPE: male, North Dakota, Nelson the damaged plants (scarred, 38%; unscarred, 33%). Co., Petersburg, 48.00206Њ N, 97.97222Њ W, 4 June 1998, Based on census data, the percentage of males over ex. Scolochloa festucacea, coll. J. Cronin. ALLOTYPE: all 3 yr was 34 Ϯ 5% (mean Ϯ SE; n ϭ 3 sites). One female, same data (primary types deposited in the hundred percent of the collected males were mac- 644 ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA Vol. 100, no. 5

Fig. 5. Survivorship curves for brachypterous and mac- ropterous female D. scolochloa. Mean Ϯ SE proportion alive per cage per day (n ϭ 10). ropterous (forewings extending beyond the abdo- men). In contrast, only 9.1 Ϯ 5.1% of the females were macropterous. Brachypterous D. scolochloa have wings that are too small to allow sustained ßight. In- dividuals were observed to weakly “ßutter” their forewings between stems. D. scolochloa seems to be monophagous in the prai- Fig. 6. Longevity and fecundity of newly eclosed D. scolochloa females. (A) Mean Ϯ SE days to 50% (median rie pothole region of northeastern North Dakota. Of longevity) and 100% (maximum longevity) survivorship of the 13 species of plants on which this planthopper was planthoppers. (B) Mean Ϯ SE eggs laid per female per day caged, feeding, as indicated by the presence of hon- given that it survived the day (daily fecundity) and eggs eydew, was only evident on sprangletop. Caged plan- produced over the life span of the females (lifetime thoppers on sprangletop had a median adult life span fecundity). of 6.6 Ϯ 1.8 d, whereas planthoppers on the remaining 12 species had a median life span of Ͻ1 d. Finally, all three caged sprangletop plants were heavily infested At the spatial scale of individual sprangletop stems, with planthopper eggs, but none of the other plant we detected no evidence that parasitism was density species had eggs. dependent. None of the 18 regression analyses was Brachypterous and macropterous females differed statistically signiÞcant. Moreover, there was no trend signiÞcantly in survivorship curves (Wilcoxon test: with regard to the slopes of the densityÐparasitism Z ϭ 3.52, P Ͻ 0.001) (Fig. 5). Median (number of days relationship: exactly one half of the tests had a positive to 50% mortality) and maximum (days to 100% mor- or negative slope. tality) adult life span was 23 and 21% higher, respec- Based on the 3-yr census, 2.7% of the late instars and tively, for brachypters than macropters (Fig. 6A). The 1.5% of adults exhibited a sac protruding from the difference between wing morphs was highly signiÞ- abdominal segments. Parasitized specimens were col- ϭ ϭ cant for maximum life span (t18 3.37, P 0.003), but lected and placed in small stem cages on sprangletop. ϭ only marginally signiÞcant for median life span (t18 For some individuals, a larva emerged from the sac and 1.91, P ϭ 0.072). Daily oviposition rates (eggs laid per spun a cocoon at the bottom of the cage. Wingless alive female per day per replicate) were 21% higher female dryinids emerged from these cocoons. for brachypters than macropters (Fig. 6B), but this difference was not signiÞcant (t ϭ 1.57, P ϭ 0.13). In 18 Discussion contrast, brachypters had a substantial advantage (46%) over macropters in terms of lifetime fecundity Diagnostic morphological characters that serve to ϭ (total eggs laid per female per replicate) (t18 4.31, separate D. scolochloa from similar delphacids include P ϭ 0.004). the narrow, parallel-sided frons, the curved pronotal Parasitoids. Over the course of six planthopper gen- lateral carinae, and the distinctive male genitalia. This erations, an average of 21.2 Ϯ 4.6% of the planthopper species shares some features with members of the eggs was parasitized. Two species of parasitoids were genus such as its small but relatively reared from these collections, Anagrus nigriventris Gi- robust body form, small pygofer, elongate paired anal rault and Anagrus columbi Perkins (Hymenoptera: tube spines, and ßattened simple genital styles. It dif- Mymaridae; Chiappini et al. 1996, Triapitsyn 1997). fers from Nothodelphax in its lighter coloration (most Voucher specimens can be found at the Department Nothodelphax are black), slightly larger body size, of Entomology, University of California, Riverside. broader pygofer in caudal aspect, and larger dia- Based on a subsample of parasitoids spanning all sites phragm opening, longer styles, and lack of a distinctive and years (n ϭ 64), 92% of the individuals were iden- ßange along the length of the aedeagus. Due to the tiÞed as A. nigriventris. difÞculty in placing this species, we assigned it to the September 2007 CRONIN AND WILSON:BIOLOGY OF NEW SPECIES OF DELPHACID PLANTHOPPER 645 genus Delphacodes (sensu lato), recognizing that its had an effect on plant performance (e.g., stem height generic placement will be reassigned upon revision of and ßowering frequency), even in high-density situ- the North American Delphacodes. ations. However, it would be premature to conclude This is the Þrst species of delphacid planthopper that sprangletop does not suffer damage from D. scolo- known to feed on S. festucacea, which is very patchy chloa. Long-term or cumulative effects of herbivory in its distribution, limited to the margins of ponds, and impact on seedlings have not been addressed. drainages, and wet depressions. In the prairie pothole Studies with P. dolus and P. marginata have revealed region of North Dakota, farmland is the primary in- signiÞcant impacts on host plant Þtness, especially in tervening habitat. In the habitat in which this study areas where the hostÐherbivore interaction is rela- was conducted, prairie cordgrass, the host for a similar tively recent (e.g., Ͻ 100 yr; Olmstead et al. 1997; delphacid, crocea (Van Duzee), can be Daehler and Strong 1995, 1997; Garcia-Rossi et al. found growing adjacent to sprangletop along pond 2003). Of course, ecologically similar species of plan- margins. D. scolochloa has a very similar biology, life thoppers, such as the pests Delphacodes kuscheli Fen- history, and parasitoid fauna to that of the well-studied nah and N. lugens, have a tremendous impact on their members of the genus Prokelisia (P. marginata, P. do- hosts (Kiritani 1979, Brentassi and Maldonado 2002, lus, and P. crocea). All four species are found in wet- March et al. 2002). lands, and they are monophagous on their host plants As is typical for delphacid planthoppers, D. scolo- (Denno and Grissell 1979, Denno et al. 1987, Holder chloa is host to egg parasitoids in the genus Anagrus. and Wilson 1992, Cronin 2003a). Nymphs are the over- A. nigriventris, the dominant egg parasitoid (account- wintering stage, with individuals seeking refuge in the ing for an estimated 92% of the parasitized hosts), is a leaf litter or rolled dead leaves or sheaths of standing common and widespread North American species vegetation (Denno 1977, Cronin 2003a). Eggs are laid (Chiappini et al. 1996). A. columbi, was known from in the subepidermis, but D. scolochloa is unique in that only a few specimens and localities (Chiappini et al. its eggs are laid predominantly in the stems of its host. 1996), but recently it has been discovered in P. crocea For all species, feeding and oviposition sites com- eggs in northeastern North Dakota (Cronin 2003b). P. pletely overlap. crocea and D. scolochloa share both Anagrus parasi- As with many species of delphacids, D. scolochloa is toids at our Þeld sites in Petersburg, Co., ND, and there wing-dimorphic (Denno et al. 1991). Females are pre- is evidence that apparent competition occurs between dominantly brachypterous, whereas males are almost these two planthopper species (Cronin 2007). Appar- entirely macropterous. P. dolus females are also pre- ent competition is a type of indirect interaction in dominantly brachypterous, but the opposite pattern which one species has a negative effect on another is observed for P. marginata and P. crocea females. species mediated through a shared natural enemy MarkÐrecapture experiments with macropterous and (Holt 1977; Holt and Lawton 1993, 1994). Interest- brachypterous D. scolochloa conÞrm the importance of long wings to both within- and among-patch move- ingly, 50 km to the east, where S. festucacea is un- ments (J.T.C., unpublished data). Not only was the common, P. crocea is only parasitized by A. columbi rate of spread within a sprangletop patch signiÞcantly (Cronin 2003b). Members of the genus Anagrus are higher for macropterous females, but colonization of important natural enemies of pests in a variety of ˆ isolated patches located Ͼ5 m away was predomi- agricultural crops, including rice (Otake 1970), corn nantly by macropterous females. (Liljestrom and Virla 2004), sugarcane (Saccharum For D. scolochloa, there is a signiÞcant trade-off officinarum L) (Metcalfe 1972) (Poaceae), grapes between dispersal ability and Þtness. Adult maximum (Vitis spp.; Vitaceae) (Settle and Wilson 1990, En- life span and lifetime fecundity of macropters were glish-Loeb et al. 2003), sugar beets (Beta vulgaris L.; reduced by 21 and 46%, respectively, in comparison Chenopodiaceae) (Meyerdirk and Moratorio 1987), with brachypterous individuals. Such trade-offs are and apples (Malus domestica Borkh.; Rosaceae) also evident in P. marginata and P. dolus (Denno et al. (Teulon and Penman 1986). 1989) and with numerous other wing-dimorphic spe- Parasitism of D. scolochloa eggs was modest, aver- cies (e.g., Roff 1984, 1986; Zera 1984). Because of the aging only 21%, and there was no evidence of spatial Þtness costs associated with macroptery, evolutionary density-dependent parasitism at the scale of individual theory suggests that should exhibit reduced stems. The absence of density-dependent parasitism dispersal in persistent as compared with temporary contrasts with the Þndings for D. kuscheli (Liljestrom habitats (Roff 1990, Denno et al. 1991). Moreover, and Virla 2004), but it is typical of the pattern for many Denno et al. (1996) found a signiÞcant negative rela- planthoppers and (Cronin and Strong tionship between dispersal capacity (macroptery 1990, 1994; Cronin 2003a). rates) and habitat persistence for P. dolus and P. mar- NymphalÐadult parasitism by dryinids is rare, aver- ginata (for reviews of other insects, see Roff 1990 and aging only Ϸ2%. Stiling and Strong (1982), Stiling et al. Denno et al. 1996). A priori, we therefore might expect (1991), and Cronin (2003b) found similarly low levels that P. crocea and D. scolochloa exist in relatively of parasitism for Prokelisia spp. With regard to para- ephemeral and permanent habitats, respectively, in sitoid assemblages, the two prairie planthoppers (D. the Great Plains. This prediction remains to be tested. scolochloa and P. crocea) have less diversity than the Despite the dominance of D. scolochloa as an her- coastal Prokelisia in that they lack strepsipteran para- bivore of sprangletop, we found no evidence that it sitoids. Along the gulf coast of Florida, up to 20% of the 646 ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA Vol. 100, no. 5 nymphs are parasitized by koebelei Pierce Clayton, W. D., and S. A. Renvoize. 1986. Genera Grami- (: Elenchidae) (Stiling et al. 1991). num: grasses of the world. Her MajestyÕs Stationary Of- In summary, we have identiÞed a new species of Þce, London, United Kingdom. delphacid planthopper in North America whose biol- Cronin, J. T. 2003a. Movement and spatial population struc- ogy, life history, and natural enemy complex are sim- ture of a prairie planthopper. Ecology 84: 1179Ð1188. ilar to other well-studied nonpest grass-feeding Cronin, J. T. 2003b. Patch structure, oviposition behavior, delphacids. It exists in a highly fragmented wetland and the distribution of parasitism risk. Ecol. Monogr. 73: 283Ð300. environment, feeds on a novel host plant, and is pre- Cronin, J. T. 2007. Shared parasitoids in a metacommunity: dominantly brachypterous. This species also serves as indirect interactions inhibit membership in a reservoir for two Anagrus parasitoids that could po- local communities. Ecol. Monogr. (in press). tentially be useful in biological control programs. Ow- Cronin, J. T., and K. J. Haynes. 2004. An invasive plant ing to an extraordinary base of ecological research on promotes unstable host-parasitoid patch dynamics. Ecol- grass-feeding delphacids, we have the opportunity to ogy 85: 2772Ð2782. examine how differences in key life history parame- Cronin, J. T., and D. R. Strong. 1990. Density-independent ters or habitat structure inßuence various ecological parasitism among host patches by Anagrus delicatis: ex- processes. For example, we plan to conduct a com- perimental manipulations of hosts. J. Anim. Ecol. 59: parative analysis of the metapopulation dynamics of P. 1019Ð1026. crocea and D. scolochloa that occupy the same habitat Cronin, J. T., and D. R. Strong. 1993. Substantially submaxi- (prairie potholes) but that differ fundamentally in mal oviposition rates by a mymarid egg parasitoid in the laboratory and Þeld. Ecology 74: 1813Ð1825. dispersal ability (J.T.C., unpublished data). We also Cronin, J. T., and D. R. Strong. 1994. Parasitoid interactions can explore differences in population dynamics be- and their contribution to the stabilization of Auchenor- tween species that live in highly fragmented (P. crocea rhyncha populations, pp. 400Ð428. In R. F. Denno and and D. scolochloa) versus relatively large continuous T. J. Perfect [eds.], Planthoppers: their ecology and man- habitats (P. dolus and P. marginata) and the conse- agement. Chapman and Hall, New York. quences of shared parasitoids between sympatrically Cronin, J. T., and D. R. Strong. 1999. Dispersal-dependent occurring planthopper species. oviposition and the aggregation of parasitism. Am. Nat. 154: 23Ð36. Cronin, J. T., K. J. Haynes, and F. Dillemuth. 2004. effects on planthopper mortality, dispersal and spatial Acknowledgments population dynamics. Ecology 85: 2134Ð2143. Daehler, C. C., and D. R. Strong. 1995. Impact of high her- The following people assisted with the Þeldwork: R. Bea- sler, J. Geber, T. Hanel, S. Jorde, M. Szymanski, A. Widdell, bivore densities on introduced smooth cordgrass, Spar- and M. Williams. K. Thompson (U.S. Fisheries and Wildlife tina alterniflora, invading San Francisco Bay, California. Service) granted us permission to work at sites 100 and 109 Estuaries 18: 409Ð417. (Waterfowl Production Areas), and D. and J. Ralston gra- Daehler, C. C., and D. R. Strong. 1997. Reduced herbivore ciously allowed us to conduct research on personal property resistance in introduced smooth cordgrass (Spartina (site N29-1). Special thanks to S. V. Triapitsyn for identifying alterniflora) after a century of herbivore-free growth. and providing mounted specimens of Anagrus species. This Oecologia (Berl.) 110: 99Ð108. work was supported by The University of North Dakota, ND Denno, R. F. 1977. 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