Used in: Diversity of Life, Structures of Life (Alternate Investigation)
Madagascar hissing cockroach - Gromphadorhina portentosa
Background. Phylum Arthropoda is subdivided into a dozen or so classes of organisms, including spiders, isopods, millipedes, centipedes, crustaceans (crabs, shrimps, and their kin), and insects. Class Insecta, the largest class of organisms on the planet, is subdivided into 26 orders, one of which is Orthoptera. Members of the Orthoptera include grasshoppers, katydids, crickets, mantids, walkingsticks, and cockroaches. They all develop through incomplete metamorphosis, starting life as a tiny immature replica of the adult, and progressing through a series of nymphal instars leading up to adulthood.
The principal player in the Diversity of Life Course is the Madagascar hissing cockroach. These magnificent insects are large, sleek, clean, slow-moving, and sexually dimorphic. And they hiss. Some students may resist handling them initially, but as they see others in their group handling the roaches, they will gain confidence and join the fun.
There are hundreds of species of cockroaches worldwide. They are essentially nocturnal scavengers, opportunistically eating fruits, grains, and decomposing plant debris. Few cockroaches fly, but many are incredibly fast runners. The hissing cockroach, however, one of the largest of its group, is a plodder, never moving quickly enough to startle a person or to escape.
The Madagascar hissing cockroach is a large, wingless cockroach with a life cycle that is somewhat different from other roaches. The female gives birth to live young after carrying the eggs and newly hatched nymphs for about 60 days. She can give birth to 30–60 nymphs at a time. The nymphs molt six times over the next half year or so before reaching maturity. Hissing cockroaches live 2–5 years.
You can identify male and female roaches by their thorax. The male has a prominent pair of ridges on the top/front of his thorax just behind his head, which are sometimes described as "horns"or "eyebrows." The female has only a slightly raised ridge.
Unlike most of the orthopterans, roaches are silent, with the notable exception of the hissing roach. It hisses by drawing air into the abdomen through spiracles on both sides of the fourth segment, and then forcing it out with a fairly loud hiss.
Hissing cockroach sources. Contact a local high school or college life-science department to see if you can get a gift or a loan of a dozen cockroaches. Pet stores sometimes have them for sale, and biological supply companies usually sell them as well. You might also search the Internet for Madagascar hissing cockroaches. A surprising number of sites offer roaches for sale. Shop around—prices vary widely. Also be aware that currently some states will not allow hissing cockroaches to be shipped into the state (Florida for example).
What to do when they arrive. Release roaches into a prepared container with plenty of ventilation but with a tight lid, as they are quite strong and can otherwise escape.
Caring for cockroaches. Hissing roaches need food, water, warmth, and cover. Use a terrarium as the habitat; its size will depend on the number of roaches you will be housing.
Before the investigation. In preparing for the food-preference part of the investigation, put your roaches on short rations. Remove food and water sources 2 or 3 days before that part. The roaches can go without food for 2 or 3 weeks, and without water for a week. Make sure they are not deprived of access to food and water for longer than 5 days.
Breeding. If you are interested in breeding your cockroaches (a good idea, as they can be costly to acquire!), set the terrarium up as described, but cover the bottom with soil rather than sand. Keep the terrarium soil and bark slightly moist (not wet) at the end away from the food, water, and heat. Hissing cockroaches give live birth, and the newborns seem to thrive in a slightly moist environment.
What to do with them when the investigations are completed. If at the end of the course you have no desire to maintain the colony, try to find a colleague, biological supply house, or zoo to take your colony. The roaches are valuable, and you should easily find them a new home. If you are left with no alternative besides euthanasia, bag and label the colony and place it in a freezer for a couple of days. Cockroaches should never be released locally.