January 20. 1893 J 



SCIENCE. 



31 



AN INTERESTING SENSORY ORGAN IN CERTAIN PLANT 

 LICE. 



BY JOHN B. SMITH, SC D., RUTGERS COLLEGE. 



During the season of 1890 plant-lice were unusually abundant 

 and destructive on a number of cultivated crops in New Jersey, 

 and I devoted some little time to the study of the more tiouble- 

 some species, presenting the results, in popular form, in Bulletin 

 No. 72 of the New Jersey Agricultural College Experiment Sta- 

 tion. One of the matters that attracted my attention more par- 

 ticularly was the peculiar pitting of the antenn». These pits 

 and tubercles, as they have been indifferently called, are well 

 known ; but they have been often treated as merely sculptural 

 features, and no special importance has been attributed to them. 

 In my examinations of the structures I recognized them as sen- 

 sory in character; but was not then and am not now able to specify 

 their exact function, since they differ from what are usually de- 

 scribed as the tactile and olfactory organs. The appended figure, 

 showing the pittings of the antenna of the peach-louse, will serve 

 to illustrate the appearance of the structures. 



of all, as I expected. I found the antennal pittings present, and 

 was not unprepared to find that they differed from the viviparous 

 winged forms in their somewhat greater number and distinctness. 

 I was disappointed to find in the oviparous female no modifica- 

 tion of the simple larval type; but, as I was in search of some 

 character that would always distinguish this particular form 

 without recourse to the primary sexual structures, I examined 

 all parts of the insects minutely, and was rewarded by finding on 

 the posterior tibise a series of sensory pittings exactly similar in 

 structure to those of the antennae in the male. I found that these 

 structures differed in each of the species examined, in size, ar- 

 rangement, and number, and the character is probably as little 

 variable here as it is in the antenna. Myzus cerasi was the only 

 species in which I had any number of specimens for examination, 

 and in this I found that the tibial pitting does not appear until the 

 insect becomes sexually mature. 



To ascertain whether other species showed the same structure, 

 I wrote Dr. C. V. Riley, asking whether he had observed it or 

 could inform me as to its presence or absence in other species. 

 Recently he very kindly replied as follows: '• I have not yet been 

 able to examine all the material at hand, but I can say that I have 

 verified your interesting discovery in tlie following species: The 

 pits are present in Aphis mali, A. pruni, Myzus iiahaleb, Siphono- 

 phora rosce, Siphonophora sp. on rose, Callipterus sp.? on oak, 

 in PliyllapTiis fagi, and in Melanoxanthus salicti. I do not find 

 them present in the following genera: Schizoneiira, Glyphina, 

 Pemphigus, and Phylloxera, while in Laehnus they are not at all 

 well developed or distinctly observable. This list, so far as it 

 goes, would, therefore, show that they occur in what may be 

 looked upon as the higher forms, and are absent in the Pemphi- 

 gincB and Phylloxerince.'' 



I have not seen any mention of the structures above described, 

 and am less than ever able to attribute a function to them. 

 Finally, I desire to express my obligation to Dr. Riley, who not 

 only examined the species mentioned in his letter, but also sent 

 me the sexed specimens on which my studies were first made. 



Peach Louse : — a, Antenna of young louse ; 6, First long joint of winged 

 form ; c, Second long joint, ; d, Third long joint; e, Whip-joint; /, Sensory pit 

 of antenna, from top ; g. Same, from side. 



I found that in all the wingless forms of all the species exam- 

 ined by me one type only was present. There is a single large 

 pit. surrounded by a little group of small pits, on the last or whip- 

 joint and, usually, a single large pit near the tip of the penulti- 

 mate segment. This structure never changes in character while 

 the insect remains wingless, whether it is newly-born or has 

 reached a point where it reproduces its kind agaraically. It con- 

 tinues also throughout the pupa state; but as soon as the winged 

 form is assumed a very decided change appears, and every spe- 

 cies shows a pitting peculiar to it. It may involve all the joints 

 or only one may be modified ; but, whatever the type, it is in- 

 variable withiu specific limits, and I have not found thus far 

 any two species in which the pitting is identical. It may be 

 that where a species is dimorphic, or where there are migratory 

 and sedentary forms, that each form may have peculiarities of 

 structure; but this I do not know. 



At the time I made the studies above mentioned, 1 had neither 

 miles nor oviparous females of any species before me, and not 

 until the fall of 1892 was I in position to examine sexed individ- 

 uals carefully. I was curious to find whether any further modi- 

 fications appeared in the true sexes, and whether the wingless, 

 oviparous females shared in the larval type of structure. I ob- 

 tained males and females of Aphis brassicce, Siphonophora cticur- 

 bitcs. S. rosce, Myzus cerasi, and Phorodon hnmiili. In the males 



THE INDIANA ACADEMY OF SCIENCE. 

 The eighth annual meeting of the Indiana Academy of Science 

 convened in the rooms of the State Board of Agriculture, Capitol 

 Building, Indianapolis, Jnd., Dec 38, 1892, and continued through 

 the 29th. The president was Professor J. L. Campbell of Wabash 

 College, Crawfordsville, Ind. The meeting was one of universal 

 interest. The attendance was large; the list of papers showed 92 

 titles, almost all of which were read. 



The officers chosen for the year were: President, J C. Arthur, 

 Purdue University, Lafayette, Ind.; vice-president, W. A. Noyes, 

 Rose Polytechnic Institute, Terre Haute, Ind.; secretary, Amos 

 W. Butler, Brookville, Ind.; assistant secretary, Stanley Coulter, 

 Purdue University, Lafayette, Ind.; treasurer, C. A, "Waldo, De- 

 Pauw University, Greencastle, Ind.; auditors, Thomas Gray. Rose 

 Polytechnic Institute, Terre Haute, Ind.; W. S. Blatchley, High 

 School. Terre Haute. Ind.; programme committee, L. M. Under- 

 wood, DePauw University, Greencastle, Ind.; W. A. Noyes, Rose 

 Polytechnic Institute, Terre Haute, Ind. 



The arrangements for the spring meeting the third week in 

 Mav contemplate a two days' session in the picturesque and inter- 

 esting region in Park County, closing with a session Friday even- 

 ing at Terre Haute. 



The editors presented their report and also the first volume of 

 the Academy's Proceedings ready for distribution. The volume 

 contains the papers of the last preceding meeting together with 

 an account of the field meetings, a bibliography of all papers read 

 before the Academy since its organization in 188.5. tngether with 

 reference to the place of publication of each. 



The following papers were presented : — 



Notes on the Reproduction and Development of GrinnelJla 

 Americana Harv. , M. A. Brannon ; Evidences of Man's Early Ex- 

 istence in Indiana, from the Oldest River Gravels along the White 

 Water River, A. W. Butler: On the Construction of a Sensitive 

 Galvanometer, Benj. W. Snow; Some Facts as to the Varying 

 Conditions of Rock Deposits as Observed in the Hudson River 



