1861. 



NEW ENGLAND FARMER. 



211 



For the Ncto EngUxnd Farmer. 

 MICROSCOPIC RESEARCH. 



ExTEiCTS PROM Dr. Harris on "Insects afpectinq Fruit 

 Treks." 



SWOLLEN BRANCnES OF THE APPLE TREE. 



"On the 31st of May, the Hon. M. P. Wilder 

 sent me some pieces of the limbs of the apple 

 tree, which were singularly enlarged in diameter 

 to the extent of several inches. Tlie specimens 

 were carefully examined by Prof. Asa Gray and 

 myself, without insects, their punctures, or their 

 tracks being found therein." 



WARTS OR EXCRESCENCES ON PLUM TREES. 



"These have been attributed by many persons 

 to the puncture, or to the presence of insects 

 therein. I have not been able to find one or the 

 other in the incipient warts, or in their immediate 

 vicinity." 



PLUM TREE INSECTS. 



" The Plum Weevil Curculio continues to baffle 

 all attempts to exterminate it. The succulent 

 warts of the plum tree provide for it abundant 

 resources in default of plums, its more appropri- 

 ate food. We may save our crop of plums by 

 covering the tree with fine netting." 



We find in these extracts the frank "opinion" of 

 Dr. Thaddeus William Harris, v/ho has given to 

 the world the best and ablest "Treatise" on En- 

 tomology ever written by an American author. 

 These extracts were from his pen subsequent to 

 May, 1854, two years after his "Treatise" was pub- 

 lished, and shortly before his decease. We have 

 reason, therefore, to believe they contain the full 

 extent of his knowledge of the contents of these 

 "warts." His "opinion" is clearly expressed that 

 he "could not find punctures or insects in them, or 

 in their immediate vicinity," and he believes they 

 "constitute food for the curculio." Now that the 

 tomb has closed over his remains, must the twin 

 sciences of Entomology, Embryology, Botany and 

 Microscopy cease in their progress ? Although he 

 labored assiduously, and is justly commended for 

 doing his work well, he did not exhaust the wide 

 fields of yet unexplored scientific research and 

 development. I do not intend by these remarks 

 to detract from the just fame he has acquired, nor 

 as doubting his "opinions" expressed and quali- 

 fied, so far as he has made researches and devel- 

 opments. But I beg others, who quote him as 

 "authority," to remember that all such reference 

 must, in all coming time be considered as the 

 "authority" of "his day and generation." Oth- 

 ers who come after him may continue to tread in 

 his path, and yet find beyond the limits of his 

 journey, unexhausted fields for their researches. 

 Near the end of his journey of "research" he as- 

 sures us that he "cannot find perforations or in- 

 sects in these incipient warts." 



^^Microscopic research'^ does develop insects 

 in these "warts." They are there. And the ques- 

 tion is, what species are they ? and when does 

 their existence commence ? Fi'om the investiga- 

 tions which I have thus far briefly made, it ap- 

 pears conclusive in my judgment, that the eggs are 

 deposited in the summer, and they, or their em- 

 bryo, or the larva, remain in the "warts" until the 

 following spring or summer. My first microscop- 

 ic examination, by the dissection of these "warts," 



was made in August last. Early in the summer 

 my trees were full of fruit, but at this time, near- 

 ly all had dropped from the trees, or had become 

 mouldy and withered on the trees. Not one 

 quart of sound plums were gathered, where there 

 should have been many bushels. The "warts" 

 vary in size from a small to a large sized pin's 

 head. Nothing can be seen in the interior of 

 these "warts" with the natural vision. The mi- 

 croscope only can reveal the interior objects. 

 Curiosity induced me to attempt to count the 

 huddled living mass thus visible. According to 

 the size of each "wart" examined with the micro- 

 scope, I found^the number of insects to vary from 

 100 to 300 in each "wart." This unlooked for, 

 and wonderful development, induced me to exam- 

 ine various works at command, to obtain some 

 published description of these "warts" or their 

 contents. I was unable to find any particular 

 statement on the subject except what I have here 

 quoted. From August to the middle of Novem- 

 ber, I continued weekly to watch, expecting fur- 

 ther development, but up to the latter period they 

 continued in their secluded position, and if any 

 change was visible, it was only a very slight in- 

 crease in size. Since the middle of November, 

 they have only exhibited the torpid appearance of 

 all insects during their winter or hibernating con- 

 dition. To test the fact of their retaining vitali- 

 ty during the several cold spells this winter, I 

 have repeated my examinations. January 2, '61, 

 while the ground was covered with snow, and the 

 thermometer IG'* below freezing point, I made a 

 minute microscopic examination, and at the time 

 made the following record : — 



[I see no change in these larva insects during 

 the two months since our cold weather first com- 

 menced. At first view as now seen, they are 

 torpid and motionless in the cavity or centre of 

 the "wart," and appear like a cluster of minute 

 eggs. At this time I renewed previous experi- 

 ments, such as applying warmth to incite anima- 

 tion. They were exposed in a warm room, and 

 from its heat and the sun's influence combined, 

 they became animated in half an hour. This re- 

 veals conclusive evidence, that, in this larva state, 

 they are thus hibernated. The genial warmth of 

 spring will, judging from the above experimental 

 tests, bring them from their hibernation ; and 

 their future development or chrysalis changes 

 will open a new door for further entomological 

 or other scientific investigations by which their 

 genus may be determined and described.] 



This development I have made by my own as- 

 siduous "microscopic research." I have good 

 reason to believe, from what Dr. Harris says of 

 those "warts," that it is a new embryological dis- 

 covery, yet undescribed by any entomologist or 

 microscopist in America. 



Certainly Dr. Harris, from his extensive knowl- 

 edge, would doubtless have given extracts, if oth- 

 ers had described these insects, and no one would 

 hardly think of searching beyond his writings for 

 the priority of such an embryological record. I 

 have, however, perused several works of foreign 

 and American publication, none of which have 

 given particular records of these "warts." These 

 "warts" are clustered round the base of that part 

 of the limb forming each year's new wood, and 

 vary from 10 to 15, making 1500 to 2000 insects, 

 subsisting suctorially upon this portion of the 



