94 



Thus, theoretically, it is uot impossible that the severe frost which 

 occurred in Florida may be followed by au extension of some Coccidte 

 northward, owing to the repeoi>ling of the trees by a race derived from 

 the exceptionally frost-proof individnals which survived. Under the 

 former conditions these individuals had no special advantage and did 

 not particularly multiply. 



When a coccid abounds on a given tree, young larva? will find their 

 way to surrounding shrubs, trees, and herbs. ( )ften they must entirely 

 perish ; sometimes, as one may see in Eulecanium, they survive in a 

 stunted and distorted form: sometimes, again, they contrive to not 

 only mature but multiply. Tn the course of time there may fall on an 

 uncongenial food i)lant one or two individuals capable of surviving 

 upon it, and these will give ri.«^e to a new coh)ny, v/hich from the very 

 start differs in its average character from the parent colony, just as the 

 pilgrims in the Mayfoicer gave rise to a colony in America differing in 

 its average from the parent country, and, what is more, advantageously 

 difiering. 



These things do not recjuire ages; I am sure they are occurring con- 

 stantly within the short period of our individual lives, and have only 

 to be looked for to be seen. Herein is the explanation of certain flour- 

 ishing colonies of coccids on plants not commonly infested by them; or, 

 on the other hand, of the absence of such colonies where they might 

 be expected. In Santa Fe, to cite a case of the latter sort, AspidiotuH 

 ancylus scarcely at all leaves the box-elders to infest the closely adjacent 

 fruit trees. 



Xot only is the spreading of Coccidie from one species of tree to 

 another thus irregular, but there is even irregularity in the attacks on 

 different varieties of the same trees. It Avould be very interesting to 

 obtain fall statistics as to the varieties of fruit trees attacked by coccids 

 and see how far they coincided in different localities. INIr. Barrett, of 

 Las Cruces, ^N". Mex., gave me the following as his experience with 

 Aspidiotus perniciosus : 



Pears: Comparatively free: Flemish Beauty, not bad; Walker's Seed- 

 ling, very bad; Bartlett, not very bad; Leconte, very bad; Duchess, 

 very bad. Api)les: Ben Davis, a good many scales; Loy, almost 

 entirely free; Maiden Blush, pretty bad; Red June, hardly any scales. 

 Plums: Wild Goose, least attacked; Lombard, very bad; Abundance, 

 pretty bad; Ja^^anese, pretty bad. Quinces: j^ot bad. 



On wild plants it is verj^ remarkable how the coccids occur in isolated 

 colonies, even when the plants abound. The species on AtripUx canes- 

 cens in the Mesilla Valley are six in number, but all occur only in iso- 

 lated patches, though there is no apparent reason why the}^ should not 

 spread all over the acres occupied by the food i^lant. They have para- 

 sites, however, and I suppose they are driven from bush to bush, here 

 and there almost annihilated, a few only surviving to found new colo- 

 nies. This constant harassing might be expected to lead to the natural 



