THE PRACTICAL ENTOMOLOGIST. 



17 



require to be renewed every day as tar does. On 

 the other hand he says that "he is not aware that 

 any Tree-protector has proved entireli/ effective' in 

 preventing the ascent of canker-worms." 



But although the Editor of the Farmer concedes 

 that tar, properly applied, prevents the female moth, 

 or the "grub" as he calls it, from climbing the tree 

 to lay her eggs thereon, yet he afterwards gives up 

 tar, rosin and oil, and all the Patent Tree Protectors 

 as unavailable, and actually advises the Michigan 

 folks to cut down, burn and destroy all their infect- 

 ed trees from one end of the State to the other, by 

 virtue of a special law to be passed for that purpose, 

 "even if it takes all summer and every militia man 

 in the State to execute the order.'-' And what is 

 the reason assigned for such a course ? Simply 

 this : — 



Those grubs which do not ascend must and will lay 

 their eggs somewhere — upon the bark of the tree beneath 

 the protector, or upon something else. This spring, eggs 

 thus deposited were hatched in countless numbers; and 

 although the worms were at first scarcely more than a 

 sixteenth of an inch in length, and not so large as a cam- 

 bric needle, they immediatcty ascended the tree tn swarms ; 

 the glass grooves [of the protector] being, of course, no 

 impediment to their march. 



Now I must candidly confess that I should not 

 have anticipated this; and it certainly is most sur- 

 prising that larvse, which Nature intended to hatch 

 out on the twigs of the tree on which they feed, 

 should, when compelled by man to hatch out on 

 the ground, know enough to seek out the trunk of 

 the tree and then climb it and pass on to the twigs, 

 their normal station. Still I have no reason to 

 doubt the fact. But what then ? We have effectu- 

 ally stopped the Mother-moth from laying her eggs 

 on the tree by tarred bandages. Will not the same 

 tarred bandages, if daily renewed through the 

 hatching time, stop her children also from climb- 

 ing the tree ? Most certainly they will, if only 

 proper care be taken to whip the bandages fast to 

 the tree, so that even the minutest larva cannot 

 crawl under them. And if the tar is applied di- 

 rectly to the bark, without any intervening band- 

 age, as appears to be the usual practice in Massa- 

 chusetts, of course there is no possibility of their 

 surmounting the obstacle. 



To head the Cankerworm, therefore, effectually, 

 the trees must be tarred afresh every day from the 

 latter end of October to the middle of May or to 

 about the time that the apple-leaves are completely 

 put forth, omitting to do so on cold days in the 

 dead of winter. Call the whole nett time 150 days, 

 to be on the safe side. A man could certainly tar 

 100 trfees in an hour, which would make 150 hours 

 or fifteen days' work for saving the Apple-crop of 

 100 trees. Put work as high as you please, and 

 apples as low as you please, and the operation, 

 viewed as a question of dollars and cents, is most 

 certainly a paying one. 



Instead of advising the Michigan Legislature to 

 pass a law for cutting down and destroying all trees 

 infested by the Canker-worm, why not advise them 

 to pass a law compelling the owners of infested trees 

 to tar them as above specified ? Or — better still, 

 because more certain to be effectual — to pass a law 



organizing a paid corps of men in the infested dis- 

 tricts to do the work ? There would then be no oc- 

 casion to call out the militia. A man might shoulder 

 his rifle, if he saw the Sheriff and his posse coming, 

 axe in hand, to cut down his orchard; but he 

 would only laugh, when he saw them charging 

 double-quick upon his apple-trees, with presented 

 tar-brushes. b. D. W. 



THE GRAPE LEAF GALL-COCCTJS. 



(Pemphigus viti/olia: Fitch.) 



Br HENRY SHIMER, U. D. 



It is more than three years since my wife first 

 called my attention to a few galls on her grape- 

 vines, in the grounds of Mt. Carroll Seminary. 

 Since then I have been a close observer, of the 

 Coccus, that inhabits the gall and its enemies. Now, 

 as the insect is making its appearance in other parts 

 of the West, in vineyards, and attracting a good 

 deal of attention, it occurs to me as not improbable 

 that some extracts from my notes might be of value 

 to the public. 



The galls when first observed here were few, 

 but have constantly increased up to the present 

 time. Generally early in June a few scattering 

 galls can be seen ; but by the last of June and 

 early in July they become very numerous. In Au- 

 gust they appear in unnumbered millions, so that 

 the young leaves turn black, die and fall off, from 

 exhaustion of sap, even before the gall is fully 

 formed. 



This is the fourth year of their presence here, 

 and the leaves are covered with galls — often 5U0 

 to 1000 galls on a single large leaf. They breed 

 with alarming rapidity. Mr. Walsh, in his answer 

 to correspondents in the 11th number of the Prao- 

 TiCAii Entomologist, makes quite a generous es- 

 timate of the breeding capacity of this insect — "50 

 eggs on a rough calculation." I have many times 

 made a very close estimate by couutiug ; and al- 

 though sometimes I find as few as he does, yet 

 more frequently I find many more — as for instance 

 July 27, 1865, 500 eggs in a single gall, the parent 

 so full as not to be able to move, and laying con- 

 tinually, the act of ovipositing actually observed. 

 August 15, 1865, upon examining some of the best 

 developed galls, not visited by enemies, I find by 

 counting and close estimation, over 5U00 eggs and 

 young ones just hatched, in a single gall with but 

 one parent insect ; ' and as the young are constantly 

 leaving, to say that each parent becomes the mother 

 of 10,U00, and in another month grand mother to 

 100,000,000, is, if at all incorrect, below the true 

 estimate; and as they produce about five perfect 

 generations in one season, it needs little mathema- 

 tical knowledge to see that one parent, not affected 

 by enemies and other misfortunes, will, in a single 

 season, become the prosicnitor of 10,000,000,000 

 000,000 — a number sufficient to encompass the 

 earth 1,250,126,277 ('over one and a quarter bil- 

 lion) times; and allowing that we crowd 50 into a 

 square inch, enough to carpet all the land portion 

 of the earth from pole to pole. And all these, un- 



