Mathew L. Brust

A Synopsis of Nebraska Grasshopper Distributions

Abstract Between 2005 and 2007, 656 new county records and eight new state records were obtained for Nebraskas short-horned grasshoppers (Acrididae and Romaleidae). This represents an increase of 30% in the known grasshopper county records in Nebraska. Based on the large number of new distribution records, it appears that the previous distributions of Nebraskas grasshoppers greatly underestimated the actual distributions. The new grasshopper state records were: Boopedon gracile, Chloealtis abdominalis, Encoptolophus subgracilis, Melanoplus bispinosus, Melanoplus borealis, Melanoplus punctulatus, Paratylotropidia brunneri, and Psinidia fenestralis were obtained. These new records will aid in both grasshopper monitoring for pest outbreaks and in conservation of rare and declining species which are often habitat specialists associated with prairie ecosystems.

Immersion Tolerance in Rangeland Grasshoppers (Orthoptera: Acrididae)

Abstract Population fluctuations of short-horned grasshoppers have been linked to the interactions of numerous factors including precipitation, temperature, vegetative growth, latitude, and timing of rainfall events. In some areas, grasshopper populations decline with increased moisture, potentially as a result of direct mortality from raindrops, or from indirect factors including the increase of fungal pathogens. Grasshoppers may also become submerged by flooding events and suffer mortality from drowning. However grasshopper survival of immersion has not been quantified in controlled experiments. We tested nymph and adult survival of immersion of seven species of rangeland grasshoppers. Under laboratory conditions, the LT50 of adult grasshoppers ranged between 7.5 and 21 h, while nymphs had an LT50 of between 3 and 13 h. Survival times indicate that mortality associated with seasonal rainfall is rarely caused by immersion. The significant resistance to hypoxia by these grasshoppers is not strongly correlated with habitat association and may instead be correlated with life history traits associated with overwintering.

Biology, Habitat Preference, and Larval Description of Cicindela cursitans Leconte (Coleoptera: Carabidae: Cicindelinae)

Abstract Cicindela cursitans LeConte is a small, flightless tiger beetle with a widely scattered distribution in the Great Plains, the Ohio Valley, and the north-central Gulf Coast region. Many aspects of the life history of C. cursitans are poorly known, and the larval stages have remained undescribed until now. We designed experiments to determine specific habitat preference, female oviposition preference, and daily activity cycles of the adults. In addition, we describe the entire pre-adult life history. Adults are most numerous on moist clay soils with sparse to patchy vegetation, but they may also occur in tall-grass prairies. Females oviposit strictly in moist soils consisting of fine particles. Adults are both diurnal and crepuscular, and presumably spend the nighttime hours hiding among vegetation. Larvae occur in the same habitats as the adults and are typically clustered near the bases of plants. The larvae are the smallest of any tiger beetle species described in North America (body length of first instars = 2.6–3.2 mm, second instars = 5.4–6.7 mm, third instars = 8.4–10.1 mm) and most similar in morphology to Cicindela debilis Bates. Knowledge of the life history and habitats used by this species will allow a better understanding of its distribution and abundance, and its association with prairie habitats. This information as well as low dispersal rates may make this species useful for assessment of habitat quality and restoration success.

Sweep Sampling Capture Rates for Rangeland Grasshoppers (Orthoptera: Acrididae) Vary During Morning Hours

Abstract Rangeland grasshoppers have long been considered pests of serious economic importance and are key components of grassland food webs. Sampling protocols inform decisions to control grasshoppers. Preliminary observations while sampling rangeland grasshoppers indicated differences in species diversity and numbers captured, depending upon time of day. To test these differences, we used USDA-APHIS sweep-net sampling protocols at various times at four rangeland sites during 2006–2007 and compared mean numbers collected. Sweep sampling every hour from 06: 00 to 12:00 revealed that adult and nymphal grasshopper numbers were significantly higher at 06:00 than either 07:00 or 08:00. Captures were similar throughout the afternoon. These patterns were also observed for adults of the most common species, Melanoplus femurrubrum (DeGeer). The results of this study have important implications for rangeland pest management decisions and ecological studies that estimate insect biomass as an indicator of food availability. Our results indicate that standardized sampling of grasshoppers in mixed-grass prairie rangeland should be conducted between 10:00 and 16:00.

Observations of Oviposition Behavior Among North American Tiger Beetle (Coleoptera: Carabidae: Cicindelinae) Species and Notes on Mass Rearing

ABSTRACT Although the larvae of a large number of North American tiger beetle species have been described, little information exists on the oviposition behavior of female tiger beetles at the species level. In this study, we found that the oviposition behavior varied widely among species, with some species utilizing more than one method. We found that, contrary to many references, several tiger beetle species did not oviposit from above the soil surface by inserting the ovipositor into the soil. Instead, several species oviposited by tunneling over 20 mm below the soil surface. In addition, we outline recently used successful protocols for rearing larvae rapidly and in large quantities.

Rangeland Grasshopper Numbers and Species Composition in Nebraska: A Comparison of Region and Sampling Location

Abstract Shorthorn grasshoppers (Orthoptera: Acrididae) are the most economically important pests of rangeland throughout much of North America. Their densities are estimated using a number of methods, including sweep sampling. Economic thresholds are usually set at 8 adult grasshoppers per square yard, despite differences in range conditions associated with geography and weather patterns. Several authors have concluded that grasshopper numbers are higher in ditch areas and the economic threshold in these habitats is often set substantially higher. This study compared grasshopper numbers and species composition at 120 rangeland sites across ∼ 400 km of northern Nebraska in 2007 and 2010. By taking sweep net samples in the ditch, parallel with the fence inside the pasture, and approximately 30 meters into the pasture, we found the numbers and composition of grasshoppers differed significantly across this area. Mean adult grasshopper capture was highest in the ditch samples (22.4 ± 1.9 grasshoppers captured per 20 net sweeps) compared to fence (10.3 ± 1.0) and field samples (15.9 ± 1.6). Mean adult capture increased from east (4.8 ± 0.4) to west (25.5 ± 2.1). The same trends were observed when nymphal numbers were included in analysis. Based on these results, rangeland grasshopper sampling should be conducted more than 30 meters from the fenceline, and thresholds in roadside ditches should be higher than for rangeland pastures.

Morphological and Genetic Analyses in the Melanoplus packardii Group (Orthoptera: Acrididae)

Abstract Melanoplus packardii Scudder was described in 1897. Three additional closely-related species were later described and their status as species has been questioned on numerous occasions. We examined morphology from specimens collected in Nebraska which fit descriptions of three of the four forms and specimens that appeared to be hybrids. We found distinct morphological characters suggesting species status for M. foedus and M. packardii, but not for M. foedus fluviatilis. Examination of aedeagi of these three forms suggests that M. foedus and M. packardii are each distinct, but that the aedeagi of M. f. fluviatilis and M. f. foedus cannot be distinguished. Molecular analyses of the three groups did not produce clear separations and suggest gene exchange between these three forms may be ongoing. Together, these data suggest that M. foedus and M. packardii should be recognized as sibling species, but M. foedus fluviatilis is best considered a form of M. foedus, typically found in low lying areas.

Fishing for Tigers: A Method for Collecting Tiger Beetle Larvae Holds Useful Applications for Biology and Conservation

ABSTRACT A series of field studies examined the effectiveness of using a grass blade/stem to extract tiger beetle larvae (Coleoptera: Carabidae: Cicindelinae) from their burrows without damaging the larva or the burrow — a procedure often called fishing. We found that larvae of many species can be efficiently sampled at rates equal to or exceeding other methods. Extracted larvae have a low percentage of injury and can be assessed for parasitism and condition. They can be returned to either their own burrow or an alternative burrow where they can be re-sampled. The results of these studies indicate that fishing for tiger beetle larvae can be an effective tool for monitoring populations where larvae can be returned to existing burrows. In addition, the fishing technique allows for relocation of organisms while eliminating the impacts associated with excavating threatened species or larvae from rare habitats.

LARVAL DESCRIPTION OF CICINDELA ( DROMOCHORUS ) PRUININA (CASEY) (COLEOPTERA: CARABIDAE: CICINDELINAE) WITH NOTES ON HABITAT AND ADULT BEHAVIOR

Abstract Cicindela (Dromochorus) pruinina (Casey) is a flightless tiger beetle that was described by Casey in 1897. Since its description, it has had a diverse nomenclatural history. It occurs from Kansas and central Missouri south through Oklahoma to south Texas. Aspects of the life history are poorly known, and the larval stages have not been described. Collections of live adults from Onaga, Kansas, were transferred to a terrarium, eggs were obtained, and larvae were reared and described. Larvae were similar to other known species of Cicindela L. Notes on habitat and adult behavior were also made.

Larval Description and New Nebraska Distribution Records for Nebraska's Tiger Beetle, Cicindela nebraskana Casey (Coleoptera: Carabidae)

ABSTRACT Adult Cicindela nebraskana Casey were captured and allowed to mate and oviposit in the laboratory. The resultant larvae provide the first formal description for all instars of this species. In 2008 and 2009, C. nebraskana was found at several new locations in Nebraska as well as in a previously unrecorded county (Dawes). Observations were made on its habitat preference, seasonality, and behavior.