Hymenolepis Diminuta

H. diminuta rarely infects humans and it's primary hosts are rats. Unlike H. nana, H. diminuta requires an intermediate host to complete its life cycle. Some common intermediate hosts include flour moths, flour beetles, meal worms, and cockroaches. It is inside the body cavity of these intermediate hosts that the ingested egg by way of contaminated feces hatches and develops into a cysticercoid larva. When rats or humans eat these infected insects, the infective larva will complete its growth in the small intestine of its hosts, where within about twenty five days it will reach complete maturity. Adult worms vary in length depending on how many are present in the intestine but usually they are between twenty and fifty centimeters long. As with H. nana, eggs will be released into the external environment to complete the cycle via the host's feces. Not all the eggs may be expelled, though, and as a result autoinfection is also a probability.

 

(courtesy of CDC Division of Parasitic Diseases) http://www.dpd.cdc.gov/dpdx/HTML/Hymenolepiasis.htm

 

adult H. diminuta

(courtesy of Microraphia <http://www.micrographia.com/specbiol/helmint/platyhel/cest0100/hymenol0.htm>)

References
Tolan, Robert Jr. eMedicine. 18 Dec. 2003. 4 June 2005 <http://www.emedicine.com/ped/topic1054.htm>.
Markell, Edward et al. Medical Parasitology. Philadelphia, PA: Sanders, 1999.