162 MOSQUITOES OF NORTH AMERICA 
(Dyar) has seen a Hydra, accidentally introduced into a breeding-jar, kill a 
mosquito larva. When Hydra is abundant, as it sometimes is in ditches and 
small ponds, it may become to some extent a check upon mosquitoes. 
VERMES. 
Martirano has described a minute trematode (Agamodistomum martiranot 
Stiles, 1903) found in the body-cavity of Anopheles maculipennis in Italy. 
Grassi, in his “ Studi di uno zoologo sulla malaria” (edit. 1901, p. 197 ) states 
that both in the pupa and the imago of Anopheles a trematode is found encysted, 
and most likely this is identical with the form observed by Martirano. Since 
then these “ Distomum ” forms have been further studied. They have been most 
intelligently discussed in a recent paper by Alessandrini, who throws some light 
on their life-cycle. He believes that these distomi are the larval form of 
Lecithodendriwm ascidia (v. Beneden), a common parasite of the European bat 
(Pipistrella ewropai). The bats are infected by eating mosquitoes which con- 
tain the Distomum encysted ; the mosquito larve become infected in turn from 
the feces of the bat, containing Distomum eggs, being dropped into the water. 
The eggs hatch in the water and the larve of the Distomum enter a mosquito 
larva and become encysted. These distomi are usually found in cysts on the 
walls of the stomach or cesophagus of the imago, but sometimes they occur free 
in the body-cavity. Alessandrini thinks that the Distomum described from 
Anopheles by Schoo is the same as that of Martirano. On the other hand, he 
considers a Distomum found in Anopheles by Ruge to be the larva of a form 
(Distomum globiporum) described much earlier by Linstrow from a snail 
(Limnea ovata) and which becomes the intestinal parasite of a fish. 
Nematode parasites of mosquitoes were observed in Europe by Stiles as early 
as 1889 and were at that time already known to Professor Leuckart. However, 
no record of them appeared until the same or a similar form was discovered in 
this country, in 1902, by Dr. J. B. Smith. This parasite was described by Dr. 
Stiles as Agamomermis culicis. In this connection Dr. Stiles discussed the 
European forms as follows: 
“In the summer of 1889 I collected a number of specimens of Agamomermis 
sp. from mosquitoes of the species Culex nemoralis taken in the vicinity of 
Leipzig, Saxony. Whether they were identical with the present form I am un- 
able to state. The interesting fact may be mentioned, however, that the Leipzig 
Agamomermis was decidedly injurious to the mosquitoes. It was found in the 
abdominal cavity of larve, pupx, and adults, so that infection must have taken 
place in the water, namely, in the larval and pupal stages of the Culex. The 
infested insects were very sluggish in their movements and could usually be 
easily recognized as diseased. Many of them died from the effects of the para- 
site, and the ovaries of infected females were underdeveloped. Professor 
Leuckart informed me at that time that he had frequently found Culez 
nemoralis infected with this worm, and that during the years that the worms 
were most common the mosquitoes seemed to be less numerous.” 
Agamomermis was first found by Dr. John B. Smith in the course of his early 
New Jersey work, while examining the females of Aédes sollicitans, in order to 
determine the development of the ovaries. He saw a strange enlargement of 
