16 PARASITOLOGY. 
The antennae are composed of segments (joints 
or articles) which vary in number according to the 
species. 
The mouth parts are provided with a proboscis 
for piercing the skin and sucking blood, or with an 
apparatus for sucking up liquid substances. 
The thorax of those belonging to the order Diptera 
is provided with three pair of legs and one pair of 
wings. Those we study under the orders Hemiptera 
and Siphonaptera are provided with three pair of 
legs only. 
With regard to reproduction, the female may lay 
the ova, larva, or ova containing the larva fully de- 
veloped. 
The insect laying the ova is called oviparous 
(ova—egg, parous—to bring forth). 
The insect producing the larva is called vivipar- 
ous (vivo—living, parous—to bring forth). 
The parasite producing the egg with the larva 
fully developed within is called ovoviviparous 
THE FLIES. 
MosouiroEs—(Musca—fly, ito—small.) 
History.—Mosquitoes are found in all parts of the 
world, from the cold countries of the north to the 
hot countries of the south. One hundred and fifty 
species have been described. More than thirty spe- 
cies are found in the United States. Among the 
common species may be named the Culex Pungens, 
Cuiex Pipiens, Culex Equinus, Stegomia Fasciata, 
and Anopheles Punctipennis. 
Description.—Mouth parts provided with lancet-like 
piercing mandibles; long, slender body; delicate, 
n 
