The summer of 1999 was the second year of a survey of insect diversity at Ryerson Woods. BugCamp students at the Field Museum conducted the survey. This year the survey was conducted on a biweekly basis, using three different collecting techniques in three fields of different sizes. The purpose of our investigations were to 1) uncover differences in insect diversity and relative abundance among different sized fields, 2) determine if abundance changed over time, and 3) to generate enthusiasm for insect diversity among our students.

To efficiently sample a wide variety of insects, we used three collecting techniques (pitfall traps, sweeping and malaise traps). These three techniques covered three strata of insect types - terrestrial insects, plant dwellers, and fliers. Ryerson Woods was sampled on a biweekly basis by BugCamp students, and Jim Louderman (Field Museum) confirmed the insect identifications of the BugCamp students. He also sorted the sweep samples collected on July 28 1999. All specimens are deposited at the Field Museum.

Fields Tested
We sampled the same three fields in 1998 and 1999 (Click here for a description). in order to compare insect diversity within and between different sized fields, and to look at how diversity changed over two summers.

In an effort to uncover correlations between weather patterns and abundance of insects, weather information was obtained from the National Oceanic and Atmospheric Administration data center.

In this section we summarize some of the interesting trends from the three collecting methods in three fields. Generally, the distint collection methods trapped distinct guilds of insects. The diversity of insects is similar in both years but very different between the three fields.

Pitfall Traps
Unbaited
Pitfall traps are designed to collect ground dwelling insects. The most commonly collected ground dwelling insects in both years were Formicidae (ants) and Staphylinidae (rove beetles). The ants were Tetramorium caespitum (Pavement ant), Camponotus sp. (Carpenter ants), Lasius sp, Leptothorax sp., Stenamma sp. Solenopsis sp., and two species of Formica sp. Many of the staphylinid beetles belong to the genera Anotylus, Philonthus, and Aleocharinae (Figures 1, 2 and 3). Although rove beetles are extremely common, their numbers were much lower than the ants. The total number of ants dropped from 127 in the July 14 sample to 34 in the July 28 sample. This dramatic decrease may be due to the increased temperature in late July. Staphylinids were surprisingly numerous in the medium field on July 14, but their numbers declined like the ants in the July 28 1999 sample. The small field showed an increase in staphylinids but this difference may not be statistically significant.

 

Sweeping
Sweeping generally collects insects in the vegetation. The most common insects collected during the students' sweeping were two suborders of Homoptera and Heteroptera (Figures 5, 6 and 7). The homopterans included aphids, Scolops sp. (a plant hopper), and Draeculacephala sp. (a leaf hopper). The heteropterans included Nabicula subcoleoptrata and Nabis sp. (Damsel bugs), three species of mirids (plant bugs) and one lygaeid species . In 1999, all three fields show a gradual increase of both Homoptera and Heteroptera as the season progressed but then drop. Homoptera is most abundant throughout the season in all three fields. In the small and medium fields Homoptera are dominant. In the large field Heteroptera was most common except in the July 28 sample.

Other commonly collected insects included the Japanese beetle and thrips. The Japanese beetle (family Scarabaeidae) is an introduced pest feeding on many prairie plants and cultivated crops. Thrips (order Thysanoptera) are minute insects with very distinct sucking mouthparts and feather-like wings. They are plant feeders and commonly found on prairie plants. The thrips are so small that students often dismissed them as grass seeds. Like the Japanese beetle, thrips damage cultivated plants by their feeding and some species are vectors of plant disease.

Malaise Traps
Malaise traps are designed to trap flying insects. Syrphids (hover flies) and chrysomelids (leaf beetles) are two of the most commonly collected flying insects (Figures 8, 9, and 10). Both groups were relatively abundant in the large field but very scarce in the small field. A comparison of syrphids collected each year in malaise traps reveal very similar profiles. Chrysomelids were only trapped in the large field.

Other commonly collected insects included Tabanidae (horse flies) and Halictidae (sweat bees). Tabanid larvae are aquatic and often predaceous, some even feed on frogs. As many have experienced, female Tabanidae feed on blood. Less well known is the fact that males feed on nectar and pollen. Halictidae were the most common group from the order Hymenoptera. Halictidae are solitary bees. Their larvae live in rotting logs and act as decomposers.

A primary objective of this study was to identify differences among three different sized fields at Ryerson Woods. Greater numbers of Staphylinidae (rove beetles) were collected in pitfall traps in the small and medium fields than in the large field. This pattern may be related to the fact that the small and medium fields are more shaded with a greater number of trees encroaching, providing a more suitable habitat for Staphylinidae. The most notable baited trap collection came when a queen ant, and her workers, were trapped on 14 July 1999 in the large field. The sweep sample graphs show a general incease in the numbers of Homoptera and Heteroptera through the summer, particularly in the large field. It is likely that the sap sucking herbivorous Homoptera and Heteroptera were attracted to the prairie grasses and other plants in these fields. In the malaise traps, higher numbers of chrysomelids and syrphids were collected in the large field than either the medium or small fields. It is likely that the higher numbers of sap sucking insects attracted adult chrysomelids and syrphids. Larvae of chrysomelids and syrphids are generalist predators that may feed on these insects.

The second objective of this study was to uncover any changes in diversity and relative abundance over time. These summers were generally quite similar. However, a comparison of the temperature for the months of June and July of 1998 and 1999 show that the maximum temperature for the summer of 1999 was significantly higher. Results recorded above show that the numbers of insects collected towards the end of the 1999 collection season were lower. In all fields there was a decline in the number of syrphids and chrysomelids in malaise traps. Futhermore, the number of Heteroptera collected in sweep nets also declined.

The third objective of our study at Ryerson Woods was to generate enthusiasm about insect diversity among BugCamp students. Children living in the city have a tendency to overlook or undervalue the natural diversity of life around them. BugCamp tries to heighten childrens' awareness by providing expert information about insects and science. Students thoroughly enjoyed collecting and identifying their collections, and feeling that they have contributed to the museum. For example, at the start of each field season many of the students did not recognize thrips collected by their sweep nets. The small size of these common insects was a surprise to many students. This simple example shows how the program extended the students knowledge of insect biodiversity employing insects collected at Ryerson Woods.

Students filled out a survey at the end of BugCamp. These surveys clearly showed that students who began the summer with some misconceptions and fears about insects soon developed an enthusiasm to collect and study insects. As an example, they learned to recognize the difference between beetle families. They also learned that common cockroaches are far more common in urban areas than in Ryerson Woods. Students found the fieldwork enjoyable. Ivan Rice particularly enjoyed learning how and where to look for different kinds of insects. He wanted to improve his personal collection at home. Even the survey work, which includes collecting sweep net samples from each field, setting up and taking down the malaise traps, and pitfall and carrion traps, was performed diligently by the students. Russell Burton said it was exciting to look in the alcohol jar after a sweep to see if there was "anything good" in the sweep, like a grasshopper or an earwig.

BugCamp students sorted the sweep samples into twelve orders of insects. The pitfall traps and carrion trap samples were sorted into target groups of insects. This year students identified many insects to the family level. An appreciation for the difficult work involved in developing, and curating a collection was cultivated by this exercise. Identifying the collections to family required the use of scientific keys and some skill with a microscope. To use the keys, students had to learn some specific terms to describe insect anatomy. Issues of diversity within and between orders and families became clearer and an understanding of the methods employed to classify organisms was a result.