70 



THE AMERICAN ENTOMOLOGIST. 



name, have perfected their spores so as to dis- 

 seminate the evil. We have made no notes of 

 the precise time of the year at which the Apple- 

 leaf Cluster-cups attain maturity; but, so far 

 as we recollect, it is some time in the month of 

 July. The best practical rule will be to destroy 

 them as soon as ever the rings begin to develop 

 on the lower surface of the leaf; and if there 

 are any infected Crab-trees growing in the 

 vicinity of the Orchard, they should be cut up 

 root and branch without the least compunction, 

 and unceremoniously subjected to the purgation 

 by fire. 



y 



GALLS AND THEIR ARCHITECTS — 2d ARTICLE. 



[OONTINUED FBOM PAGE VIVTV. ] 



[ In our last number we commenced a second 

 article on " Galls and their Architects," des- 

 cribing some of the galls made by Saw-flies. It 

 was our intention to continue this article 

 through several numbers, so as to embrace cer- 

 tain galls made respectively by Gall-flies, Bee- 

 tles, Moths, Psyllas or jumping Plant-lice, Gall- 

 gnats and Mites, and thus give our readers 

 an idea of all the different groups of gall-making 

 insects. Mr. Walsh had already written the 

 article which appears below, and at the time of 

 his fatal accident was working at, and had 

 nearly completed, another on "Galls made by 

 Beetles," which will appear in our next. We 

 shall endeavor, to the best of our ability, to 

 complete the series, as nearly as possible in the 

 same manner intended by Mr. "Walsh.] 



Galls made by Gall-flies. 



[Order Symenoptera, Gyriips Family.) 



In our former Article, we described and illus- 

 trated three different galls made by insects be- 

 longing to a genus {Cynips) which peculiarly 

 infests the diff'erent kinds of Oak. We propose 

 in this chapter to give the history of two other 

 oak-galls produced by this genus of Gall-flies. 

 There is a distinct genus {Rhodites) belonging 

 to this same Family, which exclusively attacks 

 the Rose ; and another {Diastrophus) which 

 confines itself almost entirely to the Bramble; 

 besides a fourth ( Tribalia) which originates a 

 very curious many-celled gall on the tubers of 

 the common Potato. Indeed, with the excep- 

 tion of the Gallgnats (Cecidomyia) , which are 

 quite cosmopolitan in their tastes, almost every 

 genus of gall-making insects peculiarly aflTects 

 some particular genus of plants ; or — to express 

 the same fact in different language — every group 

 of gall-makers found upon a particular group 



of plants has certain structural peculiarities 

 which distinguish it from allied groups found 

 on other gi'oups of plants. In illustration of 

 this general law, we shall towards the close of 

 this chapter describe and illustrate a new and 

 perfectly distinct genus of Gall-flies, a single 

 species of which we have discovered to generate 

 a " monothalamous " or one-celled gall on a' 

 plant {Lygodesmia junced) peculiar to the 

 Northwest. 



Upon the old-fashioned theory of every spe- 

 cies, whether of animals or of plants, having 

 been created at the beginning of some geological 

 epoch, with exactly the same organization and 

 coloration and habits that it retains to the last 

 day of its existence upon this earth, it seems dif- 

 ficult to account for such a state of things as the 

 above. For example, there are already about 60 

 described N. A. species of the genus of Gall-flies 

 (Cynips) that affects our different Oaks. Every 

 one of these forms galls upon some kind or other 

 of Oak, while not one solitary species attacks 

 any other plant. Similarly in Europe there are 

 about 100 species belonging to this genus, every 

 one of which with perhaps a single exception is 

 exclusively confined to the Oak. Why should 

 this be so? Why should not at least a few of 

 these 160 gall-makers be found upon other plants 

 besides the Oak ? The old school of philosophers 

 can only reply, that it is so because Nature has 

 seen fit that it should be so. To parody the 

 language of Shakspearo, 



They have no reason but a woman's reason; 

 They think that it is so, because it is so. 



On the other hand the new school of philoso- 

 phers will reply that it is so, because myriads 

 of ages ago a single primordial Gall-fly took 

 to forming galls upon some species or other of 

 antediluvian Oak; and that from this one spe- 

 cies have gradually and slowly originated by 

 hereditary descent, through the instrumentality 

 of continual slight changes in their organization 

 and consequently in their habits, the 160 distinct 

 kinds of Gall-flies that at the present day form 

 distinct galls upon the many distinct kinds of 

 Oak that exist on either side of the Atlantic. 

 Upon this hypothesis we can sec at once why 

 these 160 Gall-flies all inhabit the Oak, and are 

 not distributed with some approximation to 

 uniformity among our Beeches, Birches, Pop- 

 lars, Willows, Ashes, Elms, Hickories, Walnuts, 

 Hackberries, Hazels, Witch-hazels, Sumacs, 

 Dogwoods, Pines, Grape-vines, False Indigos, 

 Roses, Brambles, Thorns, Plums, Cherries, 

 Basswoods, Maples, and Box-elders — all of 

 which twenty-four genera of woody plants are 

 to our personal knowledge infested by some 



