Insects and Wulfenia bullii
In October 2016, a 7-acre parcel was identified with 500–700 Wulfenia bullii (aka kitten’s-tails) plants on it. The 7 acres is bordered with oaks and the soil is sandy. It is degraded with smooth brome dominating the herbaceous community. We learned on the tour of this site that no management has been conducted on this area (M. Martin, pers. comm.). John van der Linden, Jim Hess, and Marci Hess began studying this area for insect associations. This research was made possible with a grant from Prairie Biotic Research.
The 7 acres is located in Green County, Wisconsin in Mt. Pleasant township.
Wulfenia bullii (Scrophulariaceae) is categorized as a threatened species in Wisconsin, with a coefficient of conservation of 9. It is at risk for extinction because of its restricted range. The plant stands 8-16” tall and blooms from April to July with fruiting from July to August. The plant is found in full to partial sun in dry prairies, woodland openings, bluff edges, and oak savannas preferring sandy, gravelly soil (Wisflora database; Wisconsin DNR website).
Little information exists about insect associates of W. bullii. A search of Google Scholar resulted in one study regarding pollinators of this plant (McKone, Mark J., et. al., 1995). Because this site had no history of prescribed fire, herbicide use, or other management, it was a good candidate for this baseline study.
This is a photo of the study area.
Goals and Processes
The primary goals of this project were to identify insects and other invertebrates using W. bullii and to discover the nature of these animals’ interactions with the plant. The site was surveyed once a week between February and September; observations were conducted during the day.
Protocols were drafted prior to the research beginning. Only the rearing protocol was altered, to allow for in situ rearing of Hemiptera nymphs in specially constructed bags. Except for those we bagged, all larvae, nymphs, pupae, and eggs were collected for rearing in numbered collection vials. Rearing bags left in the field had a plastic numbered tag attached to them. Photographs of the insect in the field were taken when possible.
Wulfenia bullii is an early blooming plant. Seeds begin establishing in May and by July they are fully formed and the plant begins senescing.
Taken 25 April 2017
Taken 10 April 2017
Results
Hemiptera abounded!! Attempts to rear the nymphs were unsuccessful. Many were collected and vouchered along with adults in hopes that someday identifications can be made.
This Attenuipyga platyrhynchus was found on 07 Jul 2017.
A total of 277 specimens – both plant and invertebrate – were documented (Appendix).
The best opportunity to observe insects actually using the leaves as host plants were from the three photographed caterpillars. One species was found on three occasions with documented herbivory of the leaves.
The first was collected on 18 Feb 2017 for rearing, which was unsuccessful. A possible identification received from Caterpillar Identification of North America Facebook page user was suggested as either a Spodoptera species or Noctua pronuba (Kesting-Hardy, 2017).
Spodoptera species or Noctua pronuba
The second encounter with a caterpillar occurred on 05 May 2017. Because they are similar in appearance and no identification has been ascertained, I suspect this same type of caterpillar was encountered on 21 June and again on 19 August.
This first set of 4 images if from 05 May 2017.
This caterpillar was found on 21 June 2017, Wulfenia bullii, Kittentails
Caterpillar was found on 19 August 2017.
On July 31, this 3mm caterpillar was found sharing a leaf with a Phlegyas abbreviatus. The caterpillar was not noticed when the leafhopper was collected.
On 29 May 2017, this silken webbing was observed. While the Lepidoptera larva were curling the edge of the leaf around this, this appeared toward the middle of the leaf and never curled.
Leaf and Stem Markings
Plant parts were collected and pressed as well as photographed. There were some interesting patterns, possibly herbivory, but could be mechanical or microbial damage. Whatever caused the changes in the leaf, similar patterns were observed on other leaves.
An assortment of squiggled lines, some completely cut through the leaf as in the first example and others in varying stages and depths.
This “S” shape was seen a few times.
This was a common leaf marking on Wulfenia bullii
The herbivory along with a “trail” appears on a number of leaves.
This “V” shape was documented on several leaves. The striking pattern was similar each time.
These pointed protrusions were seen several times.
An interesting pattern
Seed Heads
In February, dried seedheads were examined and found to have markings that would indicate herbivory or possible exit holes. Note the stem scar in the second photo. Fresh markings of both were noted later in the year but this shows a specific focus on the seed pod.
In May, several seedheads were discovered and appear to be home to some insect.
Stem scars
A number of stem scars were documented. There were noted in April and May.
Discussion
This study did not result in definitive answers regarding which insects are specific to W. bullii and how they use the plant. However, further research may be appropriate in regard to some insects and insect sign observed in association with the plant. Attempts to rear caterpillars feeding on kitten’s-tails were unsuccessful, leaving their identifications a mystery for now. Future efforts could focus on rearing adults from such larvae. Obtaining species-level identifications would be helpful in determining whether the larvae are polyphagous or oligophagous. Although non-arthropod factors (e.g., disease or mechanical damage) may be responsible in some cases, the finding of distorted leaves and inflorescences, a gall-like stem swelling, and obvious feeding damage to W. bullii fruits suggests the presence of herbivorous insects that were not directly observed during this study but which could be targeted by future workers. Numerous leafhoppers and a few spittlebugs were found using the plant and sucking its juices, but it is unknown if these plants were specific hosts for them.
Most of the leafhoppers were not observed feeding on the plant. As the summer progressed, the overgrowth of the plants around the kitten’s-tails made subtle observation challenging. Once they non-target plants were moved to view the kitten’s tails, most activity stopped. A chrysomelid beetle larva was the only one undaunted by my presence.
One particular aphid, Therioaphis trifolii, was observed throughout the spring and summer. The host for this aphid is clover, which was sprinkled around the research area. That these aphids were found on the W. bulli leaves probably means they crawled or fell off their host plant. In researching this, only one aphid species is known to use W. bullii as a host plant; that is Myzus ornatus (Aphids of the World website).
A few other interesting finds include an unidentified rust on a W. bullii leaf, several snails, and a variety of Syrphidae larvae and pupae. Many syrphid larvae are predaceous on aphids (Rotheray and Gilbert 1989) and so their presence on W. bullii at this site may indicate sizable populations of aphids nearby.
Many of the photos taken were placed on BugGuide in order to make these more public and allow for expert identifications; a listing of all observations and specimens with correlating info and BugGuide reference numbers can be found in the Appendix.
Acknowledgements
Many thanks to Jim Hess for assisting on every field trip, collecting insects, GPS’g areas, collecting the quick leafhoppers, and detailing the other plant life. Thanks to John van der Linden for assisting on two field trips and offering support for protocol and report writing. Special thanks to Dr. Dan Young for serving as the advisor for this project and answering numerous questions. Special thanks also to Susan Meier who sewed in situ rearing bags on a moment’s notice. We also thank members of the BugGuide online community for their valuable assistance in identifying insect specimens. This project was made possible with the generous grant from Prairie Biotic Research and additional funding from MJ Hatfield. While the results are scant, the work provides a baseline for further research on this plant and its associated insects.
All specimens from this research have been donated to the Wisconsin Insect Research Collection.
Works Cited
Aphids of the World: An Online Identification and Information Guide. http://www.aphidsonworldsplants.info/
Kesting-Hardy, Tea’, Ken Childs, and Jonathan Brusch. February 2017. Caterpillar Identification of North America Facebook page, transcribed comments to BugGuide page. https://bugguide.net/node/view/1340972
Martin, Mark, personal communication, October 6, 2016.
McKone, Mark J., Rebecca Ostertag, Jason T. Rauscher, David A. Heiser, and F. Leland Russell. 1995. An exception to Darwin’s syndrome: floral position, protogyny, and insect visitation in Besseya bullii. Oecologia 101: 68-74.
Rotheray G.E., and F.S. Gilbert. 1989. Systematics and phylogeny of European predacious Syrphidae (Diptera) based upon larval and puparial stages. Zoological Journal of the Linnean Society 95: 29-70.
Wisconsin Department of Natural Resources. No date.
Wisflora database. No date. Flora of Wisconsin; Consortium of Wisconsin Herbaria.