Introduction

The distribution of planthoppers (Hemiptera: Auchenorrhyncha: Fulgoroidea) in the eastern United States was most recently summarized by Wilson and McPherson (1980a). Excluding the Delphacidae, Wilson and McPherson (1980a) reported only 4 planthopper species from Delaware, specifically Acanalonia conica (Say, 1830, Acanaloniidae), Catonia cinctifrons (Fitch, 1956, Achilidae), Melanoliarus ecologus (Caldwell, 1947; as Oliarus, Cixiidae), and Metcalfa pruinosa (Say, 1830, Flatidae). Additional species were later reported by Kramer in his revisions of the Cixiidae, specifically Cixius nervosus (Linnaeus, 1758) by Kramer (1981), Bothriocera cognita Caldwell, 1943, and Bothriocera drakei Metcalf, 1923, by Kramer (1983), bringing the reported fauna to 7 species in 4 families.

Our objectives were to provide an abundance-based list of planthopper species found in Delaware (excluding Delphacidae) established primarily on specimen records from the University of Delaware Insect Reference Collection (UDCC) in Newark, DE; provide a measure of completeness of this inventory using the Chao1 abundance-based diversity estimator (Chao 1984) and by comparison with incidence records from adjacent states (MD, NJ, PA and DC); and begin to assess their biology by providing preliminary information regarding the seasonality of the planthoppers of Delaware. We provide an artificial key to genus and select species to allow users to recognize planthopper species in the Mid-Atlantic States more easily.

Methods

Planthopper specimens from Delaware, Maryland, New Jersey, and Pennsylvania in the UDCC were identified to species. Identification of some taxa requires dissection of male genitalia, in which case the abdomen was removed (sometimes after relaxing the specimen overnight in high humidity) and cleared for 24 hours in 15% potassium hydroxide (KOH), rinsed in water and transferred to glycerol for observation and manipulation (see, e.g., Wilson and McPherson 1980b, Bartlett and Deitz 2000). Species identification was made according to the following sources: Metcalf (1923, Derbidae except Cedusa, Dictyopharidae except Scolops and Phylloscelis, Flatidae), McAtee (1923, Derbidae: Otiocerus), Breakey (1928, Dictyopharidae: Scolops), Doering (1938, Issidae; 1939, Caliscelidae: Bruchomorpha; 1941, Caliscelidae: Aphelonema), Beirne (1950, Achilidae: Cixidia [as Epiptera]), O’Brien (1971, Achilidae: Plectoderini), Kramer (1977, Cixiidae: Oecleus; 1979, Cixiidae: Haplaxius [as Myndus]; 1981, Cixiidae: Cixius; 1983, Cixiidae: Bothriocera, Pintalia), Mead and Kramer (1982, Cixiidae: Melanoliarus [as Oliarus]), Flynn and Kramer (1983, Derbidae: Cedusa), Freund and Wilson (1995, Acanaloniidae), McPherson and Wilson (1995, Dictyopharidae: Phylloscelis). The specific identities of some taxa were confirmed by comparison with authoritatively determined specimens at the US Smithsonian Institution National Museum of Natural History (USNM), although in a few cases we examined types, or photographs of types (specifically the derbids Otiocerus signoretii Fitch, Anotia burnetii Fitch, and Anotia robertsonii Fitch from the USNM; and Otiocerus stollii Kirby and the purported type of Anotia bonnetii Kirby [but see discussion] from the Hope Entomological Collections Oxford University Museum of Natural History, OUMNH). Additional Kirby types were sought (from the British Museum, Manchester Museum, and Oxford), but are apparently missing. Females of some genera (e.g., Derbidae: Cedusa and many Cixiidae) cannot be identified to species with confidence. These specimens were tallied at the generic level and included in the specimen counts, but not included in species counts or calculation of the Chao1 statistic (see below). The artificial key to genus and select species was constructed for all taxa not requiring dissection for identification. The key was developed by modification of keys within the above listed taxonomic references. Author and year for all species is provided in table 2.

Family-level nomenclature follows Emeljanov (1999) in recognizing Acanaloniidae and Caliscelidae as independent from Issidae. Keys to families of Fulgoroidea can be found in Wilson (2005). Generic nomenclature has been updated for Cixiidae following Emeljanov (2001) and Holzinger and colleagues (2002) and for Issidae by Gnezdilov (2004).

Incidence records were listed for Maryland, New Jersey, Pennsylvania, and the District of Columbia based on literature (see below) and specimen records. Specimen records were compiled both from the UDCC and USNM collections. Specimens from Delaware were totaled by county and collection date increment. For collection date tallies, each month was divided into two increments, “early” (the 1–15th of each month), and “late” (the 16th-end of month) dates. Specimens with incomplete date information were omitted from these counts (resulting in the number of specimens tallied for seasonal data for some species to be less than the number of specimens observed). Because some species were at times found in abundance, seasonality records were tallied in two ways; complete specimen counts, and observation records where each series (all specimens recorded from a particular location and date) was tallied as a single observation.

To help assess completeness of the inventory, literature records were compiled from published sources (viz. Wilson and McPherson 1980a, Kramer 1981, 1983; Mead and Kramer 1982, Flynn and Kramer 1983, and McPherson and Wilson 1995) into a species incidence table. Specimen incidence records were compiled with literature records, but independently annotated.

Photographs were taken using a Nikon SMZ-1500 Digital Imaging Workstation with Nikon DS-U1 digital Camera and NIS Elements Imaging software (version 3.0). Line drawings were made by Kimberley Shropshire (see acknowledgements) by tracing photographs and rendering detail freehand with reference to specimens.

Total planthopper species richness for Delaware was also evaluated using Chao’s (1984) abundance based estimator of species richness calculated as Schao = Sobs + F12/2F2, where Sobs = # observed species, F1 = # of species observed by exactly one specimen, F2 = # of species observed by exactly two specimens.

Results

Among 1, 734 specimens from Delaware we observed 62 planthopper species in 27 genera and 9 families (Table 1), including 55 new state records. Not surprisingly, specimen records were strongly biased (72% of observed specimens) toward New Castle County where the main campus of University of Delaware is located. Some females in the genera Bothriocera, Cixius, Haplaxius, Melanoliarus (all Cixiidae) and Cedusa (Derbidae), representing 88 specimens, could not be definitively identified to species and these female specimens were subsequently excluded from the species tally and the calculation of the Chao1 statistic; however, one of the female Bothriocera specimens appears to represent an additional species. Specimens of Omolicna evidently represented 2 species, but we were unable to identify them or parse the species with confidence. For this reason, we have reported the specimens identified to the generic level and included them in the species count and calculations.

The most abundant species were Melanoliarus placitus (18% of observed specimens), Aphelonema simplex (10%), Acanalonia conica (9%), Flatormenis chloris (7%), and Scolops sulcipes (5%), collectively representing 49% of the specimens observed (Figure 1). However, for Aphelonema simplex there were only 5 collecting events, one of which comprised 70, and a second 69 specimens (out of 165 total observed specimens). In contrast, Metcalfa pruinosa (5%) and Acanalonia bivittata (3%) were both observed in many collecting events, but these frequently encountered species are readily recognized in the field and either avoided by collectors or not accessioned by the collection manager, and therefore are probably relatively underrepresented.

The Chao1 biodiversity estimator was calculated as 74.08 species, indicating that 12 additional planthopper species are predicted to occur. The incidence list for Delaware and adjacent states (Table 2) includes 112 taxa, of which 50 species were recorded from surrounding states with no Delaware records. In addition, 22 species from MD, 5 from NJ, 8 from PA, and 21 from DC are new state records.

The seasonality data suggests that the optimal time of year to find planthoppers in Delaware is between late June and early August (Table 1). It appears that most species have one generation per year, although the available data is sparse for some taxa. Bruchomorpha oculata, Aphelonema simplex, and Cixius nervosus may have two generations a year. It is evident from specimens collected in logs in March that Apache degeerii overwinters as adults (early record March 1: 9 specimens from 3 collection events), although the overwintering status of other taxa is not clear from this data. Records of cixiids from late April may indicate overwintering as immatures, as has been reported for cixiids in Germany (Nickel and Remane 2002).

Specimens reported incidentally by Zuefle (2006) and Zuefle and colleagues (2008) (Table 3) provide host data for 3 Delaware planthopper species. Zuefle (2006) sampled insect use of 45 woody plants that were: 1) native, 2) non-native with native US congeners, and 3) ‘alien’ plant species with no US congeners, using pesticide knock-down or vacuum sampling. Vouchers were reported in Zuefle (2006) as ‘Oliarus sablensis’ were mostly Melanoliarus ecologus (32 of 35 dissected males were Melanoliarus ecologus and the remaining 3 Melanoliarus sablensis), so we here reported her cixiids as Melanoliarus spp. The hosts for the 3 Melanoliarus sablensis specimens were Rhododendron mucronatum, Cotoneaster lucidus, and Betula pendula. Her results confirm a polyphagous host use for Flatormenis chloris and suggest that adult Melanoliarus, or at least Melanoliarus ecologus, are polyphagous on woody plants.

Systematics

Artificial key to genus and select planthopper species from Delaware and vicinity.

Discussion Biodiversity

This survey brings the known diversity of Delaware planthoppers (excluding Delphacidae) from 7 to 62, plus provides new state records for MD (22), NJ (5), PA (8) and DC (21) providing species counts for those states as 88, 74, 60 and 46 respectively (Table 2). The Chao1 estimator suggests an additional 12 species may be found in the state. State-level incidence records of 112 species (Table 2) provides some basis for speculation of which species might be missing from the current inventory, and might be interpreted to suggest that the true diversity of planthoppers in Delaware may be closer to 100 species. A better understanding of the habits and finer-scale distribution patterns would be desirable in order to construct a candidate list of species not yet detected in the Delaware fauna. However, some species detected were not previously known from the region (viz. Aphelonema histrionica, Bothriocera drakei, Bothriocera maculata, Cixius angustatus, Sikaiana harti, Poblicia fuliginosa, and Otiocerus reaumurii), suggesting that the compiled species list may yet be substantially incomplete for the combined states.

In addition to the planthopper fauna reported here, a preliminary inventory of the delphacids of Delaware suggests at least 54 species in the state, although additional taxa are likely to be found before the completion of that inventory.

Taxonomy

Cixiidae: A number of specimens presented taxonomic difficulties. In the Cixiidae, specimens that appeared close to Melanoliarus sablensis differed from that depicted by Mead and Kramer (1982: 474) by having an additional ventral process on the aedeagus and a differing arrangement (size and orientation) of the other ventral processes. Similar specimens were observed in the Great Smoky Mountains National Park (Gonzon et al. 2007). In addition to the odd specimens, a specimen much more similar to that depicted by Mead and Kramer (1982) was found. While the possibility that these specimens represent an undescribed species should be investigated, we feel it is likely that they simply represent a variant of the more conventional form, and we have treated them as the same species with respect to biodiversity estimation calculations. Also, a group of females of Melanoliarus with uniformly dark wings were separated from others because they appear to represent a species not found among the males; they were excluded from the species counts.

Emeljanov (2001) moved several Nearctic Pentastirini from Melanoliarus to Pentastiridius and Reptalus. Pentastiridius can be separated from the other two genera by having 12 teeth at the apex of the basitarsus, versus 10 or fewer in Melanoliarus and Reptalus; however, the features of Melanoliarus have not been investigated relative to Reptalus and diagnostic features separating these genera have not been defined. It is probable that Melanoliarus as currently defined is not monophyletic.

Achilidae: Species of Cixidia were identified primarily using features described by Beirne (1950), whose key emphasized color, particularly that of the face. He admitted that there was “some variation” (Beirne 1950: 186) within taxa, and key color features were often relativistic, making species difficult to distinguish without access to authoritatively identified specimens , particularly in the context of this study Cixidia fusca, Cixidia pallida, Cixidia variegata, and Cixidia septentrionalis. Unfortunately, Beirne (1950) did not describe sufficient structural features to assist in doubtful cases. A revision of Cixidia would be desirable to address ambiguities, and to describe potential new species from the southwestern US.

Dictyopharidae: The only member of Phylloscelis collected by the authors (or the senior author’s students) was Phylloscelis rubra in New Jersey on cranberry (Vaccinium macrocarpon Aiton). This genus is a good example of a taxon that is likely to be in Delaware, but has not yet been found. While there are only 4 species in the genus, and 3 in the study area (Figure 14), the species are best confirmed by genitalic features as presented in McPherson and Wilson (1995).

Derbidae: A number of taxonomic issues were found among the Derbidae, including problems separating species in the genera Omolicna, Cedusa and two genera of Otiocerinae (Anotia and Otiocerus). Specimens of Omolicna (Derbidae) could not be definitively identified to species despite there being only 4 described North American species, and only 3 of these eastern - Omolicna fulva (Van Duzee, 1909), Omolicna mcateei (Dozier, 1928), and Omolicna uhleri (Ball, 1902). While literature records suggest that Omolicna uhleri (Ball, 1902) should be the only northern species, it was evident from the genitalia of Delaware specimens that at least 2 species are present. Because the original descriptions are incomplete, and at times conflicting with subsequent authors, we were unable to determine which of the specimens were Omolicna uhleri, and whether the remainder were Omolicna mcateei, Omolicna fulva or undescribed.

The derbid genus Cedusa is diverse and its members require examination of male genitalia for identification, and even then considerable study is required. Two species within this genus were found to differ from the descriptions provided by Flynn and Kramer (1983). Cedusa kedusa bears a large bifid process on both the left and right sides of the aedeagus. For the horizontal ramus of the bifid process on the left side, Flynn and Kramer (1983: 235) state that the apex may be “…occasionally trifurcate and dentate anteapically with the number of teeth varying from none to four…”. Most of the observed specimens in this study had 4–6 teeth, but otherwise agreed with the description of this species. For Cedusa cedusa, a feature in the key (couplet 72) states that this species has the “paramere with inner ventral margin truncately incised in basal portion” (Flynn and Kramer 1983: 135); but for most of our specimens, this feature was rounded or acute. Variations (in this feature and/or details of the processes of the aedeagus) contrast to Flynn and Kramer’s (1983: 228) comment that “all specimens [of Cedusa cedusa] seen are similar to the illustration”, and have led us to consider our specimens as ‘near cedusa’ until further evaluation of the variation in this species can be made.

Species in the Otiocerinae tended to be problematic, particularly since most taxa are rare in collections. It is also a problem that otiocerines have been described primarily based on superficial color features whose diagnostic value has not been verified by reference to genitalic features. While attempting to verify our species concepts, we solicited photographs or examined type specimens of select otiocerines. We found that many of the Fitch types (deposited at the USNM) are in poor shape and greatly faded. It is likely that some of the Kirby collection had been lost (see Horn and Kahle, 1935), and 6 of 8 otiocerine Kirby types could not be located at this time (specifically Otiocerus schellenbergii, Otiocerus reaumurii, Otiocerus degeerii, Otiocerus abbotii, Otiocerus coquebertii and Anotia bonnetii [but see below]). It is clear that both Anotia and Otiocerus are in need of revision. The revision should reference genitalic features to verify species identities, provide a critical reexamination of geographic records, and (as needed) designate neotypes for the apparently missing Kirby types, although Kirby (1821) generally provided adequate descriptions. Also, based on Kirby’s (1821) description, it is possible that the balli of McAtee (1923) is the same as Kirby’s schellenbergii. While McAtee (1923) and Metcalf (1923) may have misapprehended these species, we have retained their view of these taxa until definitive evidence (esp. Kirby’s schellenbergii type) can be found.

Ten species of Anotia are reported from the United States (including species formerly in Amalopota Van Duzee, 1889, subsumed under Anotia by Fennah, 1951: 152). Of the 10 species, Anotia caliginosa Ball, 1937, and Anotia lineata Ball, 1937, are southwestern species (recorded from Arizona) and Anotia mcateei (Dozier, 1928), reported from Illinois and Mississippi, does not occur in the study area. Of the remainder, 5 (Anotia burnetii, Anotia bonnetii, Anotia kirkaldyi, Anotia robertsoni, and Anotia westwoodi) are similar in appearance in having white wings whose veins are variably bordered with dark. It is not clear how much intraspecific variation would be expected in features of wing color or pattern, and such patterns were difficult to interpret in the greatly faded Fitch type specimens (we examined types of Anotia robertsonii and Anotia burnetii). Anotia kirkaldyi and Anotia westwoodi share with Anotia bonnetii the presence of dark spots in the apical cells of the forewing, although they may be more prominent in the latter species. Anotia kirkaldyi and Anotia westwoodi can be separated with difficulty based on the presence of darkened wing veins in the former species, but these taxa are otherwise very similar and may not be distinct. Anotia robertsonii is similar to Anotia burnetii in possessing less extensive wing markings than Anotia kirkaldyi, Anotia westwoodi, and Anotia bonnetii; and in possessing dark markings on the dorsum of the abdomen, although in Anotia burnetii the markings are confined to the middorsum of segments 1–3 and in Anotia robertsonii the entire dorsum of subsequent terga (5–7 or 8).

The type specimen of Anotia bonnetii (the type species of the genus) was also sought, along with types of other otiocerines described by Kirby (1821). Kirby (1821) specified that he had a single Anotia bonnetii specimen, which he described and illustrated. The specimen photographed as the type of Anotia bonnetii (at OUMNH) is pinned and spread, missing the abdomen, both wings on the left side, and the head anterior to the eyes; but it was clear that the specimen was not the one used to describe Anotia bonnetii. We feel the type has been mislabelled, and this specimen is actually the type of Otiocerus francilloni. The specimen could readily have been mislabeled when the Oxford Museum type collection was evacuated to the cellar underneath the Ashmolean Museum during World War II. Kirby (1821: 17), reports black spots and bands (“elytris nigro punctatis et fasciatis”) for Otiocerus francilloni, with the black band interrupted, which is consistent with this specimen.

Nine species of Otiocerus are reported from the north of Mexico; two species, Otiocerus abbotii Kirby, 1821, and Otiocerus kirbyii Fitch, 1851; are not reported from the study area (but see below). We examined the types of Otiocerus signoretii and Otiocerus stollii to help confirm features attributed to these species. The type specimen of Otiocerus signoretii, at the USNM, is in rather poor condition, faded, and partially enmeshed in mycelium, but shows the pattern of spots described by Fitch (1856: 394) that was used in subsequent keys to the genus (“…four dots… placed at the angles of an imaginary square…”). Fitch (1856) also reports “…a broad dusky cloud-like stripe from the base to the middle of the inner margin, and extending thence obliquely across to the outer margin at its tip, and sending a very broad branch to the tip of the inner margin…”. In the type specimen, these marking are very faint. The type specimen of Otiocerus stollii Kirby (at OUMNH) consists of only of one front and one hind wing (evidently of the right side), but the forewing was consistent with our understanding of that species.

McAtee (1923: 47) noted within his key that Otiocerus reaumurii, Otiocerus wolfii, and Otiocerus signoretii “may be one species”. While we are confident that Otiocerus wolfii is distinct from the other taxa, Otiocerus reaumurii and Otiocerus signoretii are very similar. Because the type specimen of Otiocerus signoretii is greatly faded, we attempted to diagnose this species from Otiocerus reaumurii by the distribution of dark spots on the wing, in particular the presence of a spot in the costal cell of Otiocerus signoretii. From the available material, these species appear to differ externally mainly in the spot organization. McAtee (1923: 46–47) noted that between the two species, the vitta of Otiocerus reaumurii was broader and ‘percurrent’, and the vitta of Otiocerus signoretii was ‘forked at apex of clavus’, but we have been unable to verify these features. These species are both similar to Otiocerus stollii except for more extensive dark markings of Otiocerus stollii. Interestingly, all observed specimens of Otiocerus reaumurii and Otiocerus signoretii were female, and all observed Otiocerus stollii were male, possibly suggesting that all these species are part of a single sexually dimorphic species. However, we did not observe a sufficient number of specimens to exclude the possibility that this sex ratio was obtained by chance alone. Also, Fitch reported the type of Otiocerus signoretii to be a male, but the condition of the type specimen makes this difficult to confirm.

A single specimen of Otiocerus from Maryland was not clearly associated with any of the described species. The specimen is uniformly pale, head without markings, forewings without spots and with a very faint band. A similar specimen was found among undetermined Derbidae at the USNM. It is possible that this specimen is Otiocerus kirbyii, but we were unable to confirm this identification.

Conclusion

While the planthoppers of the eastern United States may be characterized as relatively well known from a taxonomic perspective, their faunistics and ecology remain poorly understood. Although Delaware is near the two largest insect collections in the US (the USNM and the American Museum of Natural History, both of which employ hemipterists), it is a testament to our inchoate understanding of US planthopper faunistics that this study has increased our known Delaware fauna by over 700%. The diversity of planthopper species in Delaware is expected to be relatively modest relative to other states because it is small and physiographically rather uniform, and because planthopper diversity tends to generally increase inversely with latitude (and within North America, is greatest overall in the southwest). Here we also report totals of 88 species for Maryland, 74 for New Jersey, 60 for Pennsylvania, and 46 for the District of Columbia based on a compilation of literature records and available specimens. The only other state with a modern, relatively complete, survey of its planthopper fauna is Illinois (Wilson and McPherson 1980b), which reported 150 species, of which 66 were delphacids. In comparison, the total North American planthopper fauna appears to be 12 families, 165 genera and 935 species, of which 61 genera and 338 species are delphacids, and approximately 2/3 of all US planthopper species are western (unpublished data from species checklist compiled by S. W. Wilson, L. B. O’Brien, and C. R. Bartlett). Clearly our understanding of the faunistics of US planthoppers is limited, and our appreciation of planthopper ecology remains in its infancy. Further regional investigations would be helpful in gaining a more complete understanding of the US planthopper fauna.