OF THE STATE ENTOMOLOGIST. 45 



Mode of Spreading. — The gall-lice can only spread by traveling, 

 when newly hatched, from one vine to another ; and, if this slow mode 

 of progression were the only one which the species is capable of, the 

 disease would be comparatively harmless. The root-lice, however, not 

 only travel under-ground along the interlocking roots of adjacent 

 vines, but crawl actively over the surface of the ground, or wing 

 their way from vine to vine, and from vineyard to vineyard. Doubts 

 have been repeatedly expressed by European writers as to the power 

 of such a delicate and frail-winged tly to traverse the air to any great 

 distance. " On a calm, clear day, the latter part of last June, it was 

 my fortune to witness a closely-allied species { P liy llox era oar yce folios 

 Fitch), of the same size and proportions, swarming on the wing to 

 such an extent that to look against the sun revealed them as a myriad 

 silver specula. They settled on my clothing by dozens, and any 

 substance in the vicinity that was the least sticky was covered with 

 them. With such a sight before one's eyes, and with full knowledge 

 of the prolificacy of these lice, it required no elfort to understand the 

 fearful rapidity at which the Phylloxera disease has spread in France, 

 or the epidemic nature it has assumed. Imagine such swarms, mostly 

 composed of egg- bearing females, slowly drifting, or more rapidly 

 blown, from vineyard to vineyard ; imagine them settling upon the 

 vines and depositing their eggs, which give birth to fecund females, 

 whose progeny in five generations, and probably in a single season, 

 may be numbered by billions, and you have a plague (should there be 

 no conditions to prevent that increase) which, though almost invisible 

 and easily unnoticed, may become as blasting as the plagues of 

 Egypt."* 



As early as 1871 1 showed with what facility and power the species 

 referred to in the above extract can take wing when the atmospheric 

 conditions are favorable ; and on the 27th of last September, the 

 weather being quite warm and summer-like, with much moisture in 

 the atmosphere, I witnessed the same power of flight in the Grape 

 Phylloxera. Some two hundred winged individuals, which I had con- 

 fined, became very active and restless, vigorously vibrating their 

 wings and beating about their glass cages. Upon opening the cages, 

 the lice began to dart away and were out of sight in a twinkle. They 

 have been caught in spider-webs in Europe, and I have repeatedly 

 captured them on sheets of paper prepared with bird-lime and sus- 

 pended in an infested vineyard ; and am satisfied that they can sustain 

 flight for a considerable time under favorable conditions, and, with the 

 assistance of the wind, they may be wafted to great distances. These 

 winged females are much more numerous in the fall of the year than 



♦Fifth Re^)., pp. 72, 73. 



