Harlequin Bug Observations

Lesson Plan by Tania Kim

General Information:

Location:  This can be conducted anywhere the bug has been observed. This insect tends to be found on Bladder Pod bush, and members of the mustard family. It is considered an agricultural pest on cabbage and kale, so any pesticide-free area where they farm these products is a great place to find the Harlequin Bug. There is Bladder Pod at the Scripps Coastal Reserve, the Kendall-Frost Mission Bay Marsh Reserve and many other locations.

Duration:  A few class periods to discuss the process of science and introduce the Harlequin Bug-Bladder Pod Bush system and teach identification. A possible extension here is to introduce taxonomy and have students construct dichotomous keys with the local plants or animals they are likely to encounter. Then they can use their keys in the field (to assess dichotomous key knowledge-let them use their keys for a field plant quiz). Several class periods (2-4) before the field, a day in the field and several class periods for analysis, writing, peer editing and presenting materials. Note this can be an on-going project while other material is covered.

Grade Level:  variable
This fits most readily with the process standards, especially if students are allowed to follow the entire process, from coming up with a question and predictions to writing a scientific paper and presenting their results. If taxonomy is used as an extension, with the dichotomous keys and classification levels are taught in conjunction with this unit then the standards addressing the topics will also be covered.


The students will develop their field observations skills and participate in the process of science from coming up with a question to writing up a report and peer editing.

This lesson is designed to be a very open ended lesson-with teacher guidance but not necessarily a lot of structure. Meaning the students are introduced to the system and asked to brainstorm questions or what they think. This can be an individual project or a cooperative learning activity. Structure can easily be added by telling the students which questions you would like them to address, this however takes away some of the intrinsic motivation from the students, since they are likely to be more interested in answering their own questions (even if they end up being the same you’d ask of them!). 


Become familiar with the system yourself. Talk to rangers or managers for more background or possible resources. A basic insect guide is helpful, as is a plant guide. Go out to the site to check it out. Prepare a way to introduce the system and identification of the local plants, insects and natural history background of the site to your students-such as a video or slide show. Once that is done you can use it for years to come.

Background Information

The Harlequin Bug, (Murgantia histrionica) is a member of the stink bug family, Pentatomidae. It is a brightly colored insect; black dorsally with orange markings and the abdomen is brightly colored in orange and yellow/cream. Please see attached picture for identification of the insect as well as Bladder Pod Bush. It is unclear whether this insect is native to southern California or if it was introduced. It is considered an agricultural pest of crops such as cabbage and kale. It is commonly found on all of the parts of Bladder Pod Bush. All instar (development phases of the insect) are found on the plant, and on all the above-ground parts of the plants. A Harlequin bug can spend its entire life on one bush. The insects have also been observed on other plants, such as mustards. The insects feed on the plants with their sucking mouth-parts and can cause considerable damage to the fruits. These insects will drop from the plant when threatened, feigning death. When observing Murgantia histrionica, note the different sizes seen on a given plant, the smaller ones are the young.


In the class period that students come up with questions regarding the system, ask students to choose a question they want to try to answer (preferably without discussing that with their friends-to encourage them to work for their own curiosity and not with Suzie Q’s best friend) and place them in groups. Note you can have more than one group addressing the same question. allow each group time to discuss the methods they will be employing and write it up (this can be homework). Students then turn in a list of materials they need along with their methods. This allows the teacher to advise students on their methods and modify them if need-be. Also provides a list of materials that need to be assembled. Students need to also decide on what tasks need to be done in the field, design a data sheet and division of labor.

Once all this is approved by the teacher, a background on the habitat to be visited and proper field behavior is a great idea. Remind students to not disturb the habitat, harass the animals, stomp the plants and all the typical respecting nature information.

On the day of field work-make sure students have water, hats, suncreen their materials and have a list of students with allergies. Bring a first aid kit to the field and if possible a cell phone. Then let the students find their sites-it is important to visit a place in which all groups will have access to the system without fighting for it-so it is a very good idea to speak with a manager or ranger ahead or time-or visit the site yourself (take photos and use them to introduce the system to your students). Then, monitor the students’ progress and help them with any difficulties they encounter. Also-keep them on track.
possible questions students may come up with: Average number of harlequin bugs on mustard versus bladder pod, perhaps they’ll take into account canopy area of the plant; or maybe they’ll want to know if the adults are found on any specific part of the plant more often-how about younger insects?; How long do the insects wait before dropping from the leaves?-note make sure students do not harm the insects; maybe they wonder about ratios of adults to young on different plant species. 

If your students are young or you are very limited in time assign them a question that you can easily design the experiment for and with straight forward analysis-simple means comparison. With older students consider teaching simple statistics-ask a math teacher in your school for help if you do not feel very confident with stats.

Once your students have their data, and back at school-the next day perhaps, have a discussion on analysis. Have the groups analyze their data, this can be simple graphs for comparison, to actual statistics and an introduction to statistical significance-it is up to you.

If you haven’t talked about scientific writing in your class, now is a great time. Have students write up their results. (Intro, materials, procedure, results, discussion, acknowledgements, bibliography). Students will present their results in class as a scientific meeting-another great thing to introduce them to. You can also gather the students’ papers and collate them into your class’ very own journal! (Claudia Luke of the HOST program does this with the HOST teachers and it was rewarding to see the summation of the group’s work). 

If you would rather not have a huge unit out of this, you can skip a lot of the steps and have students do observations for a given question, a class discussion of the results and leave it at that.

There is lots of flexibility with this idea, so play with it to fit your class’ needs.


These will vary depending on what the students decide to examine. However, for the most part this is intended as an observation exercise and therefore minimal tools should be required. All students will need 

  • paper and pencil
  • a writing surface
  • metric rulers (calipers?)
  • forceps or gloves (for squeamish kids)

Possible Extensions

Many ideas are given above-this is a very open ended lesson, in terms of what the students will actually try to address as well as how the teacher wants to approach it. In fact it can be done with any organism-it is a basic observation exercise.