212 CONSIDERATIONS OF CLASSIFICATION AND METHODS 



and all species of Culex under the designation Culicinae. The name of a subfamily 

 ends in "inse." Now, again, certain insects are different from others in having 

 scales on the wings. We find that not only do the Culicinae have such character- 

 istics; but the same is observed with the Anophelinae and other similar scale-wing 

 insects. All of these we term a Family and we speak of the Culicidae, meaning 

 the family of mosquitoes. The name of a family ends in "idae." Many families 

 are not subdivided into subfamilies, but are directly separated into genera. Again, 

 a genus may have only a single species. 



At times a family may be raised to superfamily rank the subfamilies then 

 becoming families. Thus the families Ixodidae and Argasidae belong to the super- 

 family Ixodoidea. The termination for a superfamily is oidea. 



When there are a number of families agreeing closely in some striking character- 

 istic, we group them together into an Order; thus, the family of mosquitoes closely 

 resembling many other families of insects in possessing a pair of well-developed 

 wings are grouped in the order Diptera; all of which resemble certain other animals 

 in the possession of a distinct head, thorax and abdomen with three pairs of legs 

 projecting from the thorax. This collection of animals we call a Class; thus, we 

 speak of the class Insecta. It will be observed that the insects have no internal 

 skeleton, but instead a chitinous cuticle, the exoskeleton. Spiders, ticks, etc., 

 resemble them in this respect, and we now apply to all such animals the wider 

 designation, Branch or Phylum Arthropoda. 



Inasmuch as the animal kingdom is divided into the branches Protozoa, Pori- 

 fera, Ccelenterata, Echinodermata, Vermes, Arthropoda, Mollusca and Chordata, 

 we see that the branch is the largest grouping we employ. To descend in the scale 

 we have belonging to the branch, the classes; to the class, the orders; to the order, 

 the families; to the family, the subfamilies; to the subfamily, the genera; to the 

 genus, the species. Occasionally a species is further divided into subspecies. 



By a type species we understand the species of a genus always re- 

 ferred to as representing the genus. 



While other species of a genus may for good reason be transferred to another 

 genus the type species is permanently in the genus. Many favor alliteration for 

 type species, as Heterophyes heterophyes. When a species is transferred to a new 

 genus the specific name goes with it. 



The male animal is designated by the sign of Mars (cf ), the female by that of 

 Venus (9). 



There are certain terms employed in animal parasitology which it is necessary 

 to understand. Among these we shall refer to the following: 



1. True Parasitism. By this is understood the condition where the parasite 

 does harm to the host, deriving all the benefit of the association. A good example 

 of this would be the hookworm infecting man or animals. 



2. Mutualism. In such an association there is mutual benefit to each party 

 of the association. An instance of this would be the presence of colon bacilli in 

 the intestines. The bacillus is furnished a suitable habitat and in return protects 

 its hDst against strictly pathogenic bacteria. 



Another example would be the oyster crab found inside the oyster shell. 



