Pacific Science (1997), vol. 51, no. 4: 413--423 © 1997 by University of Hawai'i Press. All rights reserved Larval Characteristics and Generic Placement of Endemic Hawaiian Hemerobiids (Neuroptera)l CATHERINE A. TAUBER2 AND ALAN H. KRAKAUER3 ABSTRACT: The brown lacewings (Neuroptera: Hemerobiidae) have undergone a spectacular radiation on the Hawaiian Archipelago; currently 23 endemic micromine species are recognized, 19 of which were described by Perkins and four by Zimmer­ man. Recent systematics studies, using adult morphological characteristics, placed these lacewings in the cosmopolitan genus Micromus. Two of the Hawaiian species (Micromus vagus [from Hawai'i and Maui] and M. rubrinervis [from Hawai'i)) exhibit larval characteristics indicating a close relationship with Micromus. Both species have more larval traits in common with Micromus than with other hemerobiid genera. However, until larvae from the three other genera in Microminae become available, it is not possible to designate whether any of these larval traits are synapomorphic for Micromus. The results also indicate that phylogenetic analyses of the Hemerobiidae should include all instars and that interspecific comparisons should be made on equivalent semaphoronts. OUR STUDY FOCUSES on one of Hawai'i's most micromine species and the cosmopolitan genus diverse and fascinating groups of predatory Micromus (Perkins 1899, Zimmerman 1957), insects, the endemic micromine brown lace­ but they allocated the species among three gen­ wings (Neuroptera: Hemerobiidae). R. C. L. Per­ era, Nesomicromus, Pseudopsectra, and Neso­ kins pioneered in the collection and systematic thauma. More recently, all 23 species of study of Hawaiian hemerobiids. He described micromine hemerobiids endemic to Hawai'i 23 species, which were grouped into three new were included in Micromus (Monserrat 1990, genera (Perkins 1899, 1910). Nineteen of these Oswald 1993). No study has examined whether species remain recognized, and they include the Hawaiian micromine lineage is some with heavily scalloped wings, as well as monophyletic. flightless species with coriaceous forewings and Almost all previous systematic work on hem­ rudimentary or no hind wings. Subsequent to erobiids is based exclusively on the adult stage, Perkins' work, E. C. Zimmerman added four and knowledge ofhemerobiid larvae is generally new species and compiled a comprehensive poorly developed. Nevertheless, some detailed review of the group (Zimmerman 1957). Both descriptions of hemerobiid larvae exist (e.g., Perkins and Zimmerman recognized numerous Killington 1936, 1937, 1946, MacLeod 1960), similarities between the endemic Hawaiian and syntheses ofthe scattered larval descriptions are beginning to emerge (MacLeod 1960, Veens­ 1 This project was funded in part by Regional Research Project W-185, the Undergraduate Fellowship Program of tra et al. 1990, Krakauer and Tauber 1996). the Pew Charitable Foundation, the National Geographic These investigations indicate that the compara­ Society (Research Committee), the CALS Office for tive morphology of the larvae will contribute Research, Cornell University (Morley Grant for Undergradu­ substantially to the overall systematic analysis ate Research and CALS Charitable Trust), and the Grace H. Griswold Fund (Department ofEntomology, Cornell Univer­ of the group (e.g., see MacLeod 1960, Krakauer sity). This is contribution no. 1996-024 of the Hawai'i Bio­ and Tauber 1996). logical Survey. Manuscript accepted 3 February 1997. Krakauer and Tauber (1996) described a suite 2 Department of Entomology, Comstock Hall, Cornell of traits that distinguishes Micromus larvae from University, Ithaca, New York 14853 (address for correspon­ those of seven genera representing six subfami­ dence); also Research Associate, Bernice P. Bishop Museum, Honolulu, Hawai'i. lies other than Microminae. Larvae in these J Cornell University, Ithaca. New York 14853. seven genera share many of the traits expressed 413 414 PACIFIC SCIENCE, Volume 51, October 1997 by Micromus; moreover, there are no studies of Maui (1989). Our larval specimens of M. rubri­ larvae from the three other micromine genera. nervis originated from females collected at two Consequently, it is not possible to delineate sites on Hawai'i: Krpuka Puaulu, Hawai'i Volca­ whether any of the traits are synapomorphic for noes National Park (1993), and Volcano, a small Micromus or to assign polarity to the character town east of the national park (1993). Voucher transformations. Despite these limitations, the specimens are in the Cornell University Insect suite of traits consistently separated Micromus Collection (Lot no. 1205), the Bishop Museum larvae from the other genera. And, until hemero­ (adults and larvae), and the Research Collection biid larvae are subject to a general systematic of Hawai'i Volcanoes National Park. study, a modified version of the previous com­ Field-collected adults were maintained in parison forms a useful basis for examining glass vials under a photoperiod of 16:8 (L:D); whether the larval morphology of the Hawaiian the temperature was 21 ± 1°C during the pho­ hemerobiids is consistent with their current tophase and 18 ± 1°C during the scotophase. placement in Micromus. Here we focus on two Humidity was kept high in the vials by enclosing endemic species of Hawaiian hemerobiids, them in a plastic bag containing moist paper Micromus rubrinervis (Perkins) and M. vagus towels. Adults were provided green peach (Perkins). aphids, Myzus persicae (Sulzer), every 1-3 days. Previously, the larva of only one endemic Cotton plugs in the vials, which usually served Hawaiian hemerobiid (M. vagus) was described as the substrate for oviposition, were removed (Terry 1908); unfortunately, that description is daily when eggs were observed. Larvae were not sufficiently detailed to aid in generic com­ reared individually under the same photoperiod, parisons. A subsequent reference to an endemic temperature, and humidity as the adults. The diet hemerobiid larva (Williams 1931) is question­ consisted ofgreen peach aphids and occasionally able because the associated figure depicts a pea aphids, Acyrthosiphon pisum (Harris). green lacewing larva (Neuroptera: Chrysopi­ Although psocids (but not aphids) are endemic dae). Therefore, it is not surprising that the inclu­ to Hawai'i and presumably compose the usual sion of the endemic Hawaiian brown lacewings prey of most Hawaiian hemerobiids, several within Micromus was based exclusively on Micromus species (including M. vagus) consume adult characters. nonnative aphids in the field (Zimmerman Several Hawaiian insect taxa show single­ 1957). All individuals were examined daily for island endemism (Howarth and Mull 1992); M. molting or cocoon spinning. rubrinervis follows this pattern. This species is Larvae were killed in KAAD solution (a mix­ known only from mid- to high-elevation forests ture ofkerosene, alcohol, glacial acetic acid, and on the island of Hawai'i (Zimmerman 1957). In dioxane [see Stehr 1987]) and stored in 95% contrast, M. vagus has been recorded from all ethanol. Specimens of each instar were cleared six of the main islands and an array of habitats, in a solution of 10% KOH for 2 days. Lateral including, during the first half of the century, incisions were made in large specimens to facili­ lowland agricultural fields (Terry 1908, Wil­ tate the removal of internal structures that did liams 1931, Zimmerman 1957). Adults of the not clear adequately. Subsequently, larvae were two species are superficially similar, but differ moved to clearing fluid (lactic acid, phenol, and in wing venation and terminalic structures. glacial acetic acid) mixed with double stain (lig­ nin pink and acid fuchsin), where they remained for 1 day at 50°C. Larvae were then passed through a series ofethanol solutions (70%, 85%, MATERIALS AND METHODS 95%, at least 2 hr in each solution), followed We examined larvae (F I offspring) of M. by a 1:1 or 1:2 mixture of 95% ethanol and vagus that were reared from adults collected glycerin for 1 day. Finally, they were mounted in Klpuka Puaulu, Hawai'i Volcanoes National in glycerin on depression slides. Park, on the island of Hawai'i (1993) and in the The following structures were measured Waikamoi Forest Reserve, Ko'olau State Forest before specimens were cleared (Figure 1): width (north slope of Haleakala, 1050-1300 m), on ofhead (greatest head width, including the eyes); O.5mm FIGURE I. Micromus vagus third instar, dorsum. 416 PACIFIC SCIENCE, Volume 51, October 1997 length of head (medial, excluding jaws); length Wesmaelius, Drepanepteryx, and Micromus, it of jaws (straight-line distance from distal tip to extends beyond the cervix. The head capsules medial margin of the base); length offlagellum; of most of our specimens of M. rubrinervis and length of pedicel; length of scape (medial); M. vagus are protruding (Figure 1); any variabil­ length of labial palpi (excluding mentum); ity in this character is an artifact ofpreservation; length of distal segment of labial palps; body the head capsules of the living larvae were not length (tip of mandibles to tip of abdomen); retracted. length of cervix; width of cervix; widths of pro­ (2) ANTENNA: JAW RATIO (third instars): (a) thorax, mesothorax, and metathorax (maximum > 1.2, (b) < 1.2. Unlike those in Sympherobius, values); length ofprothoracic, mesothoracic, and Psectra, Drepanacra, and Megalomus, the metathoracic tibiae; length ofprothoracic, meso­ antennae of Hemerobius, Wesmaelius, Drepa­ thoracic, and metathoracic