256 ENTOMOLOGICAL NEWS. [Oct., '02 



these, there is very little to assist one to recognize the species. 

 We may take Kcrmes qnercus as a fair example. Geoffroy 

 seems to give the best description, and in fact all which aided 

 me in the identification of the insect (which was sent to me 

 by Dr. Reh) ; it reads something like this : 



' ' Chermes quercus reniformis. L,e Kcrmes reniforme de Chene 

 (the reiiifarm Kermes of the oak) ; as to its form it differs from 

 that of all the others, approaching the form of a kidney and 

 having a brown color." 



The above could be well said to have been the first period in 

 the description of the Coccidae. The second period commenced 

 with Signoret who paid considerable attention to structural 

 characters, viewed by transmitted light by the use of a com- 

 pound microscope, and gave measurements of antennal joints 

 and other structural characters. The measurements however 

 were only approximate, that is, he measured as it appeared to 

 Ije to his eye, viewed through the field of the microscope. A 

 number of authors since and some at the present time, I am 

 sorry to say, use the same method. It is not at all accurate as 

 will be .seen below. Several lengthy descriptions have been 

 made using a multiplicity of words, and with very little reference 

 to the structural characters which are specific in the species un- 

 der consideration, thus making the description valueless. Some 

 give in detail the changes which take place in the life circle of 

 the insect and omit often the characters present in the adult 

 stage, too much attention being given to the young forms, 

 giving shape, color and size to the adult female only. 



The third (and present) period seems to have begun in 1897 

 when the use of the micromillimeter was brought into service 

 more exten.sively. Prof. J. D. Tinsley was the first to meas- 

 ure the legs and antennae sy.steniatically, but some European 

 authors have sometimes given measurements in /'. Prof. 

 Theo. D. A. Cockercll was the first to introduce the "For- 

 mula " of the measurements of the antenme in 1895 ; it is con- 

 structed by enumerating the joints in the order of tlieir lengths, 

 beginning with the longest, and bracketing together those of 

 equal length. He was the first to plot out " curves" for the 

 antenna; which Ih a rapid method for comparing data. 



