Insect Diversity on Mount Mansfield

Introduction in the 1991 VMC Annual Report. The 1993 season represents the third The 1991 and 1992 Lepidoptera consecutive year of the insect surveys were concentrated on the biodiversity program on Mount larger bodied "macro-Lepidoptera". Mansfield. The surveys are designed to These moths are mostly larger-bodied record the taxonomic composition and species and are generally more abundance of selected insect groups, accessible to precise identification. and monitor seasonal and annual Many of the "micro-Lepidoptera", in changes taking place. contrast, are poorly known or require considerable specialist expertise for The major taxa being surveyed accurate identification. In 1993 the comprise the ground dwelling Carabidae Lepidoptera survey was extended to (Coleoptera) from pitfall traps, the include all species as a preliminary nocturnal Lepidoptera (moths) from attempt to characterize overall diversity light traps, and the macro-Hymenoptera for Lepidoptera at the survey sites. The (wasps, bees), and Diptera (flies) from terms "micro-Lepidoptera" and "macro- Lepidoptera " do not comprise natural canopy malaise traps. Preliminary species lists for these groups were phylogenetic groups, and are used here presented in the 1991, and 1992 VMC for descriptive convenience only. Annual reports. Lepidoptera were collected from Methods a single light traps operated for only one night per week at each site. The Sampling was continued at the objective of surveying all Lepidoptera established survey sites in a sugar species was to characterize species maple forest at 400 m elevation diversity for the larger taxa (families). (Proctor Maple Research Center; Individual species identification was a PMRC), a mixed hardwood forest at secondary consideration. Most species 600 m (Underhill State Park; USP), and listed in this report are, however , a sub-alpine balsam fir forest at 1160 identified with reasonable confidence. m near the southern summit of Mount Some micro-Lepidoptera, in particular , Mansfield (MMS) . will require further evaluation to confirm identifications. Because of the Five permanent 20 m diameter difficulty of distinguishing very small plots were established at each site with species from external features the a malaise trap installed in the canopy of number of species listed under- one dominant sugar maple or fir tree estimates the total number of species (sub-alpine site) in each of the four collected at the traps. outlying plots. Six pitfall traps were installed around each plot at 60° Results intervals and a single light trap was located in the center plot. The 1993 The Carabidae, Hymenoptera, and survey covered the period from 6 May Diptera are sorted, identified, and to 5 October. A detailed account of entered into a computer database by J. field and laboratory methods is outlined Boone. The data for these groups will 140 be statistically analyzed to evaluate species were most abundant at PMRC. differences in site diversity. A number of Lepidoptera at Lepidoptera diversity Mount Mansfield exhibited distinct A total of 391 species were identified bivoltine generations. The geometrid (Table 1 ) .The pattern of taxonomic Campaea perlata feeds on many representation at the family level was different trees and shrubs including similar at each of the sites, the principal birches, maples, poplars and firs, and is contrast being in the total numbers of present at both lower elevation sites. It individuals (Figs. 1-3). Family diversity was common over a six week period for species and individuals was during mid-summer, and again in the dominated by (in descending order) the early fall (Fig. 6). Noctuidae, Geometridae, Tortricidae, Pyralidae. Most of the remaining In contrast, the three species of families were represented by very small Plagodis are usually present in low numbers of species and individuals. Of numbers, and with limited flight periods the dominant families, the Tortricidae (Fig. 7). The seasonality of P. and Pyralidae represent micro- fervidaria comprised early spring and lepidopteran groups. The total number mid-summer generations separated by of families was similar in the lower an interval of eight weeks. The adult sites with five more families being emerge of the other Plagodis species present in PMRC. The greatest contrast occurs within this interval, suggesting involves MMS with only 10 families that their larval development in the and just over 200 species for anyone second generation is completed within family. three or four weeks. All three species are known to feed on a range of Seasonal patterns hardwood trees. It is not practical to present seasonal patterns for all species documented in Two species that are distributed this report. The following examples over all sites, but more abundant at illustrate some of the periodicities higher elevations, are the geometrids observed. The patterns do not Dysstroma citrata (Fig. 8), and D. distinguish between emergence and truncata (Fig. 9). The infrequent persistence of adults, except for groups records of D. citrata are late summer such as the Saturniidae where adults and early fall, while D. truncata is are non-feeding and do not survive the abundant over the latter two months of period between light trap sampling. summer, particularly at site 2. Both species may feed on herbs or tree The flight periods of the forest species. tent caterpillar (Malacosoma disstria) (Fig. 4) and eastern tent caterpillar (M. Two species of saturniid moths americana) (Fig. 5) represent an activity are present at the lower elevation sites, period of about five weeks, but with but only in low numbers (Fig. 10). They most moths appearing within a single are of potential interest for long-term week, possibly suggesting a high level surveys because they represent of a of synchrony in emergence. Both group of moths that have in the past 141 demonstrated apparent sensitivity to adults, and are actively feeding in the chemical pesticides. Some species have spring and fall. Some species are rarely, become locally extinct or greatly if ever, attracted to lights, and best reduced in numbers due to pesticides or collected using bait (fermenting other environmental impacts. The alcohol/sugar /fruit) . adults are non-feeding (atrophied mouthparts) and because the light trap Long-term comparisons of light specimens are always in perfect trap data may be most informative on condition, the seasonal records can be species diversity and abundance for the directly related to weather conditions at macro-Lepidopteran groups Noctuidae, the time of collection. The larvae of Geometridae, Notodontidae, Arctiidae, both species are recorded feeding on a Saturniidae, Sphingidae, Lymantriidae wide range of host trees. Lasiocampidae, Drepanidae, and Limacodidae. These are now well In contrast to the saturniid documented for Mount Mansfield, and moths, the fall hemlock looper can be identified accurately by visual Larnbdina tisce!!aria has a very broad examination for most species. There are flight period, and is present in a few exceptions which require closer considerable numbers Although a pest morphological examination, and the species in some areas of the genus Eupithecia, in particular, will northeastern United States and Canada, require further genitalic examination for there is no indication at present that a comprehensive listing of species. the numbers recorded on Mount Mansfield are responsible for specific Micro-Lepidoptera are unlikely to levels of damage to trees. It is be intensively surveyed on a regular probable, although not confirmed, that basis because they require greater the moth feeds on a range of hardwood resources than are available for this species on Mount Mansfield. study. However, if it were practical, regular surveys of the Tortricidae would be desirable because this is one of the Discussion most diverse families of micro- Lepidoptera collected from the Mount The Lepidoptera diversity patterns are Mansfield light traps, and it includes only preliminary, particularly with species that are known to feed on tree respect to the micro-Lepidoptera which and shrub foliage, including some with may be less effectively caught by the pest status. light traps. Even if they are attracted to the light, the plexiglass vanes may not The seasonal patterns of be effective in disrupting the flight of Lepidoptera may be strongly influenced these small moths. Long-term by weather patterns, particularly if the documentation will be necessary to weather influences the number of confirm the current results, and other moths attracted to the light traps. collections techniques may be desirable Casual observations suggest that cool to survey those species not attracted to and/or very wet (heavy rains) weather the lights. Some species of Noctuidae can reduce the number of moths. The and various other families overwinter as limited sampling of one light trap per 142 site and for only for one night per week Coleoptera. The identification of micro- may result in misleading patterns if the lepidoptera was assisted by Mike trap night coincides with poor weather . Sabourin (South Burlington), with Replication and/or multiple sampling specialist confirmations contributed by nights is desirable, but not feasible at a number of systematists at regional present. In the future the seasonal institutions. Data collection was periodicities of moths could be assisted by Carlos Saltero (University of compared with both weather and tree Vermont Research Program. Data phenology to develop a predictive processing and

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