164 Annals Entomological Society of America [Vol. XIV, 
As the interest in helminthology grew these scattered ref- 
erences were rapidly multiplied. This is not surprising when we 
consider the amazing diligence with which the early workers on 
animal parasites. pushed their work. Ten years before his death 
Bremser wrote that he had with his own hand dissected over 
25,000 animals in search for endo-parasites. The collection 
under his direction, which he was constantly working over, 
contained specimens from 50,000 hosts. 
Rudolphi in 1819 lists 29 species of insects in which had 
been found nematode worms. Von Linstow 1878, in his Com- 
pendium der Helminthologie, lists 220 insect hosts and to these 
he added 43 species in his ‘‘ Nachtrag”’ of 1889. 
Some of the most significant of the observations along this 
line were made by Stein, in the course of his comprehensive 
work on the female reproductive organs, published in 1847. He 
found many instances of larval nematodes and cestodes encysted 
in his specimens. 
In a most significant paper, published in 1853, he calls 
especial attention to these finds and suggests that the larval 
worms which he found were taken up with their insect host by 
some other animal in which they reached maturity. His most 
noteworthy discovery was that in the body cavity of the meal- 
beetle, Tenebrio molitor and its larve, there were occasionally to 
be found numerous microscopic cysts enclosing a tapeworm-like 
head. These he found in all stages from the recently liberated 
embryo to the completed cysticercoid, and he suggests that 
they might be the larve of a tapeworm of cats, dogs, rats or 
mice, or even of man. In the light of our present day knowl- 
edge, there is every reason to believe that Stein had found the 
larval stage of Hymenolepis diminuta of rodents and occasion- 
ally of man. As we shall see later this tapeworm has as inter- 
mediate host a variety of insects, including Tenebrionid beetles. 
The first complete life cycle of a parasitic worm involving 
an insect as intermediate host seems to have been worked out 
by Leuckart in 1867 for Protospirura muris (Spiroptera obtusa), 
a small, round worm found in the stomach of mice. The eggs of 
this worm are discharged with the droppings of mice, and are 
picked up by meal worms and the escaping embryos make their 
way to the body cavity of the larva and become encapsuled, 
there to remain until the insect is eaten by a mouse, within 
