﻿160 EIGHTH ANNUAL REPORT 



Where this egg is naturally laid I have not yet ascertained, but in all probability 

 it is carried into or near the ground by the impregnated parent. The young hatching 

 from it is the normal agaraous female ; for, though I have not yet hatched this impreg- 

 nated egg of vastatrix, I have succeeded in doing so with that of Rileyi, and Balbiani 

 long since did so with that of quercus. I am led to think that, once impregnated, the 

 female carries her egg into the ground, because in 1873 I found females whose abdo- 

 mens, instead of being filled with numerous small (.'gg?, were distended with a single 

 large one ;* and, though I was puzzled to interpret the fact at the time, I have no doubfc 

 now that 1 then had under my eyes the true, impregnated female here described, and 

 that I overlooked the obsolete mouth. 



The habits of these sexed individuals, as I have been able to observe in both the 

 Grape and American Oak species, are similar to those recorded by Balbiani of the Eu- 

 ropean Oak species. The male is quite ardent, more active than the female and some- 

 what longer-lived. 



The complete natural history of the Grape Phylloxera may now be considered 

 established. A full biological view of the species exhibits to us no less than five differ- 

 ent kinds of eggs : 1st, the regularly ovoid egg, 0.25 mm. long and half that in diame- 

 ter, of the normal, agamic and apterous female, as it is found upon the roots ; 2d, the 

 similar, but somewhat smaller ^gg of the gall-inhabiting mother ; 3rd, the $ egg from 

 the winged mother, rather more ellipsoidal, aud 0.50 mm. long when mature ; 4th, the 

 (^ egg from same, i- less in length and rather stouter; 5th, the impregnated egg, just 

 described, 0.32 mm. long and still more ellipsoidal. We have also the singular spectacle 

 of an egg from the winged mother increasing from 0.34 mm. (its size when laid) to 0.40 

 mm. (its size just before hatching ;) giving birth to a perfect insect 0.40 mm. long, and 

 this in-^turn, without any nourishment, laying an egg 32 mm. long. A being is thus 

 born, and, without food whatsoever, lays an egg very nearly as large as that from which 

 she came. 



From observations here recorded I would draw the following conclusions : 



1. We can no longer entertain the hope of any practical good from the knowl- 

 edge of the nidus chosen by the winged mothers, as the destruction either of these or 

 of their eggs — scattered as they are on the leaves all throvigh a vineyard — is out of the 

 question. The objects are too small to be practically searched for, and it is virtually 

 impossible to prevent the spread of the disease in this stage. We might almost as weli 

 try to prevent mildew by the destruction of the invisible floating spores that must at 

 times pervade the atmosphere of a vineyard. The hope entertained by Lichensteia 

 that the winged mothers would congregate and be attracted to some particular plant 

 must, I think, be abandoned. 



2. The only preference shown in this respect would seem to be for those leaves 

 that are most downy or tomentose ; and from this view of the case we get another 

 probable reason why the vaiieties of Lubrusca which are characterized by an abund- 

 ant downiness on the under surface of the leaves suffer most from the insect. 



3. Having already had the young from the impregnated egg of Rileyi hatch in 

 about a fortnight after it was laid ; having shown in previous writings that this species 

 winters in the larva state, and not in the impregnated egg as does the European 

 quercus; and, remembering, further, that vastatrix re&embXes Rileyi in wintering as 



* One fact, which is not noAV interpretable, but may have a significance in future, I feel constrained 

 to record in this connection. It is tliat, in examinmg vastatrix, I liave occasionally met with degraded 

 ?'s (underground mothers) in which the abdomen, instead of containing numerous small ova, was 

 well nigh tilled with a single, much larger, egg. Every observed fact leads to others yet unknown and 

 unsuspected ; and the full history of Phylloxera has yet to be written.— 0th Rep , p. S7. 



