520 A. CENTURY OF PROGRESS IN THE NATURAL SCIENCES 



some peculiar form such as the genus of the lac-producing scales, the genus of the 

 cochineal insects, the genus whose only known member produces the white wax 

 much used in China, and the genus of the strange "ground pearls." But it was 

 not until 1868, more than a hundred years from the time of Linnaeus, that Si- 

 gnoret and Targioni-Tozzetti — the one in France, the other in Italy — added 

 greatly to the known forms. In a catalogue published in 1868 Signoret listed 

 a total of just over 300 known species, which he placed in the scale insects, and 

 at the close of his work, in a list of genera, many of them established by 

 him, he records approximately 70 names, of which a few are snyonjans. It is 

 from this work that any especially serious attempt to understand the scale in- 

 sects dates. 



It was perhaps this work which stimulated a number of workers on this 

 group during the period from 1869 to 1900. These included Comstock, whose 

 reports on scale insects were the first examples of an approach to clear and un- 

 derstandable illustrations of a small number of species. There was Maskell, work- 

 ing in New Zealand, who, in a series of papers beginning in 1878 and ending in 

 1898, described a large number of forms, few of which, unfortunately, can be 

 identified from his descriptions and very inadequate illustrations. There was 

 Cockerell, in the United States, who described numerous species and whose work, 

 almost entirely without illustrations, did little more than indicate that scale in- 

 sects existed on certain hosts in certain areas. There was the work of Newstead, 

 continued long after 1900 and best known through his Monograph of the Coc- 

 cidae of Britain, which appeared in two volumes (dated 1901 and 1903) and at- 

 tained a standard of usableness closely approaching the standard with which 

 we might be satisfied today. There was the work of Green, which culminated 

 long after 1900 in the five volumes of his Coccidae of Ceylon, a work most beau- 

 tifully but inadequately illustrated. There was the work of Leonardi, begun in 

 the 'nineties and continued until his death in 1918, which never rose much above 

 the minimum of enduring value. And there were various minor students whose 

 work was in no way notable. 



Altogether, however, the number of species and genera that were at least 

 brought to notice greatly increased, rendering the publication of a comprehen- 

 sive catalogue desirable. In 1903 such a catalogue was published, the resiilt of a 

 huge labor of compilation carried through by Maria Fernald. In this she listed 

 1,514 species that had been named up to that time. This publication marked a 

 most important step in the development of our knowledge of this group and is 

 still an invaluable work of reference. 



After 1900 there followed a period in which a considerable number of students 

 of the scale insects appeared and the literature grew rapidly. From 1906 to 

 1915 supplements to the Fernald catalogue were published, the last of these, by 

 E. E. Sasscer in 1915, bringing the total number of described species to more 

 than 2,100 names. Since that time there has been no accounting, but the niTmber 

 of described species must now total almost or quite 3,000. 



It is clear that the scale insects, now rather generally accepted as a super- 

 family, the Coccoidea, are actually an enormous group. If we may form any 

 valid opinion on the basis of the number of species that have been described 

 from parts of the world where collecting has been done with some care, it may 

 be surmised that the named species number perhaps no more than one tenth and 



