ENTOMOLOGY

RELATION OF INSECTS TO THE PARASITIC WORMS 55adult moth by Grassi and RoveIIi were carried over from the larval stageof the insect. He failed in his attempts to infect Forficula auricularia,Blatta orientalis, and Blattella germanica. He also failed to infect.beetles belonging to the species Blaps mortisaga, but succeeded easily ininfecting the· adults of Tenebrio molitor. The larvIE of this latter beetleaccording to Joyeux are incapable of acting as intermediate hosts ofH. diminuta. He was able to infect the larvIE of rat fleas and of Pulexirritans and Ctenocephalus canis. In these insects the embryos of H.diminuta begin immediately to develop into cysticercoids and do not waitfor the transformation of the larval fleas into adults, as Joyeux found inthe case of Dipylidiwm canimum, the embryos of which apparently liedormant in the insect until after it transforms into the adult stage. Inthis country Nickerson (1911) has reared the cysticercoid in myriapods,Fontaria 't'irginiensis and Julus sp., fed on the eggs of the tapeworm. Hefailed in his attempts to infect meal worms.It is evident that infection of the definitive host with H. diminutarC'Iults from swallowing infested insects, the latter having become infestedas a result of swallowing the eggs contained in the feces of animals harboringthe tapeworms. As a parasite of man in the United States, so far asavailable statistics show, H. diminuta ranks about third in frequencyamong the tapeworms, the beef tapeworm (Tamia satftnata) being themost common, and the dwarf tapeworm (H. nana) being next. Evidentprophylactic measures are those directed toward the destruction of ratsand mice and the avoidance of the ingestion by human beings of thevariousinsects that may serve as intermediate hosts, especially the protectionof farinaceous foods from insect infestation.Hymenolepis nana (Siebold, 1852) Blanchard, 1891Hymenolepis nana (the dwarf tapeworm) is a very common intestinalparasite of rats and mice and is of rather frequent occurrence in man,especially in children. In the United States it ranks second to the beeftapeworm in the order of frequency among the tapeworms of man. Itslife history has not been fully worked out. Grassi (1887), however, hasfound that cysticercoids develop in the intestinal villi of rats that havebeen fed the eggs of the dwarf tapeworm. According to his view thecysticercoids later break out of the villi into the lumen of the intestineand grow into mature tapeworms. The rat thus acts both as intermediateand definitive host of the dwarf tapeworm, the parasite beingspread from one rat to another 'through the medium of the eggs passedin the feces. The dwarf tapeworm, according to Grassi's version of thelife cycle, is an exception to the rule among tapeworms that the adultstage occurs in one species of animal a,nd the larval stage in another