Oct., '02] ENTOMOLOGICAL NEWS. 257 



To illustrate the difference in measuring with the eye and 

 with the micromillimeter, we will take for an example I£u/c 

 caniuni persica, a species little understood. The antennae 

 when viewed by transmitted light and measured by the obser- 

 ver's eye, joints one and two appear to be equal ; three is about 

 as long as one and two together, but when measured with a 

 micromillimeter scale they are very different, thus joint (i) 

 52, (2) 40, (3) 48// long, the width of joints (i) 64, (2) 48, 

 (3) 36. The eye seems to be deceived by the broad first joint, 

 joint three is very much thinner and hence seems to the eye to 

 be much longer than one. 



Again take the common mealy bug (so called) of our green- 

 house Dadylopiiis citri. Prof. Comstock described the antennse 

 and says joint 8 is longest, twice as long as 3, 2 and 7 equal, 5 

 and 6 equal, and 4 is shortest. I have tried my eye with the 

 following results : 8 and 3 longest ; 3 distinctly shorter than 

 8 ; I and 2 next longest and about equal, 5 a little longer than 

 4, 6 and 7 .shortest and equal. 



A careful measurement with a micromillimeter gives the fol- 

 lowing results : joints i, 2, 3, 4, 5, 6, 7, 8 : 96, 88, 96, 68, 80, 

 81, 44, 104. 



The formula of Comstock 's measurements with the eye 8 3 

 (27) (56) 4 omitting joint i ; of those by my. self with the eye 

 8 3 (i 2) 5 4 (6 7) and with the micromillimeter 8 (13) 2654, 

 7. This I believe is the first time that the true measurements 

 of the antennal joints of Dactylopius dfrihave been given. It 

 .should be said, however, in the study of Coccidae that meas- 

 urements in // should be made after the insect has been boiled 

 in caustic potash and washed with cold water, also again after 

 being hardened with alcohol and finally after being mounted in 

 balsam. Distinct differences will be found to exist in the three 

 stages, both in the length and width of the antennal joints. 

 There are some genera of Coccidae in which the specific charac- 

 ters are only found in the young larvae. Kermes is an 

 example, but I venture to say that all our Kermes can be cor- 

 rectly determined from the characters found ta exist in the 

 adult female .scale alone ; but in the Lecaiiinm and Pu/vhiaria 

 so far as I can now .see, there is very little in the young larvae to 



