522 A CENTURY OF PROGRESS IN THE NATURAL SCIENCES 



was a third genus named, and not until 1871 was a fourth genus established. As 

 late as 1904 only seven genera had been named and one of these did not belong 

 to the sucking lice. Even as late as 1908 only 65 species were known. In 1916 

 a catalogue of the group listed about 120 species and since that time the number 

 of known species has almost, if not quite, doubled. 



Until about 1915 the study of this group was handicapped by the lack of any 

 knowledge of the proper preparation of specimens for study, but about that time 

 methods became available which now make the examination of species of this 

 group quite simple. 



Correlated with the difficulties of the study of species has been the curious 

 history of the development of a system of classification. As already noted, Lin- 

 naeus included the sucking lice, along with many other forms, in the genus 

 Pediculus, which was placed in the order Aptera. They were then placed by 

 Fabricius in the order Antliata, along with another miscellaneous group of 

 forms. Then, in 1806, Latreille established the order Parasita for the biting lice 

 and sucking lice. In 1815 the order Anoplura was named for the lice by Leach. 

 In 1874 the sucking lice were placed by Giebel in the Hemiptera, and since that 

 time various ordinal names have been employed for them. The idea that the 

 sucking lice are connected in some way with the Hemiptera long persisted. 



Of recent years the principal difference of opinion concerning them is whether 

 they should be united once more with the biting lice into a single order or 

 whether two orders should be maintained for these two groups. The writer holds 

 that they should be separated into two orders, the name Anoplura being em- 

 ployed for the sucking lice. 



The writer's interest in this group, continued over many years, culminating 

 with the publication in 1951 of a volume, entitled The Sucking Lice. The general 

 classification of the group into families and subfamilies is still unsatisfactory 

 and must remain so until a larger number of species have been found. 



The Mallophaga or Biting Lice 



The order Mallophaga is another group of mostly quite small forms which 

 can be studied only from microscopic preparations. Fortunately, most of the 

 species are quite darkly pigmented and do not need to be stained, but they do 

 call for proper preparation if their characters are to be appreciated, and they, 

 like other microscopic insects, have suffered from the lack of interest in the de- 

 velopment of methods of preparation. 



The Mallophaga are primarily bird-infesting forms, only a relatively few spe- 

 cies occurring on mammals, and these bird-infesting species have never aroused 

 quite the same feelings of repugnance which have commonly been felt toward 

 the sucking lice. Since birds have been favorite subjects for study, the Mallo- 

 phaga have attracted a good deal of interest. 



The early history of the group, however, is involved with the sucking lice 

 and it was not until 1806 that a distinction between the two groups was noted, 

 although they were placed in the same order. Some time between 1840 and 1845 

 Burmeister named the order Mallophaga and it has Ijeen maintained quite con- 

 sistently ever since. 



Three great events in the group's early history should be recorded. In 1842 



