October, '10] COCKERELL ON COCCID^ 429 



that those on the last joint are shorter, none longer than the joint 

 itself. The antennal curve (based on the lengths of the joints) is 

 nearly as in occidentalis, ehrhorni and cockerelli, but is not like innum- 

 erabilis, the third and fifth joints being much longer. (For innumer- 

 abilis I have two composite curves, based on 15 and 9 antennae 

 respectively, measured by King.) 



I supposed at first that my insect would prove to be P. innumerabilis 

 hetheli King, ^ described from Colorado, and at first stated to be from 

 Betula, but really from Alnus. This hetheli form, however, really seems 

 to be innumerabilis, and at any rate its special characters are not 

 found in suhalpina. 



P. vitis verrucoses King, found at Hamburg on Betula verrucosa, has 

 the last antennal joint shorter, marginal hairs 40 yu., tibia 188 /w, and 

 tarsus 96 (data from King). It does not appear to be our species. 

 Mr. J. G. Sanders (Journ. Econ. Ent., Dec. 1909) has stated that 

 P. vitis, occidentalis and innumerabilis are all one species. There is no 

 doubt that his illuminating experiments throw much fight on the 

 variability -of P. innumerabilis, and its adaptability to different plants. 

 Indications of all this had been given by other writers, especially King 

 (Psyche, May 1901), and it must doubtless be admitted that we have 

 too many names in this group. Newstead treats P. ribesice as a vari- 

 ety of vitis, but nevertheless when he made experiments similar to 

 those of Mr. Sanders, transferring the insects to twenty different 

 plants, he met with no success, although the larvae were seen to 

 hatch. It thus appears that in the P. vitis groups there exist one or 

 more very polyphagous species, and others which are virtually con- 

 fined to one type of plant. The monophagous forms should no doubt 

 be classed as true species, although they may very closely resemble 

 the common widespread vitis or innumerabilis. As to the identity of 

 P. vitis with innumerabilis and occidentalis, I am far from positively 

 asserting that Mr. Sanders is wrong; but if he has data proving it, he 

 he has not yet published them, and until he does so I am wholly 

 unwilling to accept his dictum as final. Apparently these things have 

 small but real distinctive characters, and I fear that in these and other 

 instances there will be a tendency to " lump " uncritically, partly 

 because it saves much trouble, and partly as a reaction against too 

 much " splitting." 



P. innumerabilis is common in Denver. If all the insects now 

 discussed are one species, it is just possible that the eggs or larvae 

 were brought to Tolland by a bird, a distance of about 30 miles. I 

 can hardly doubt, however, that subal'pina is native, and if not a form 



^Pulvinaria innumerabilis hetheli: was described from " Colorado." I learn from 

 Mr. Bethel that it was obtained on Alnus tenuifolia at Grand Lake, Middle Park. 



