Academy of Science. 27 



OBSERVATIONS ON THE USE OF THE ANTENNA OF POLYPHILLA 

 VARIOLOSA .—HARRIS. 



BY PROF. F. H. SNOW, OF THE UNIVERSITY OF KANSAS. 



Penikese Island, the site of the Anderson School of Natural History, is one of the 

 group known as the Elizabeth Islands, situated about half way between Martha's Vine- 

 yard and the city of New Bedford, some sixteen miles from each of these localities. This 

 almost barren island contains about eighty acres of land, and is entirely destitute of shrubs 

 and trees, thus affording a very unpromising collecting-ground for an entomologist. 



While walking over the eastern elevation of the island, after sundown, on July 13, the 

 writer obtained two or three specimens of an insect belonging to the Scarabsean family 

 of Coleoptera, described by Harris as Melolontha Variolosa, but now referred to the genu^ 

 Polyphylla. Harris speaks of this beetle as "occurring abundantly in the month of July 

 at Martha's Vineyard, and in some other places near the coast;" but as "rare in other 

 parts of Massachusetts." In general appearance, mode of development, and habits, it 

 resembles the common May beetle, Phyllophaga fusca, Frohl. The larva and pupa stages 

 of its existence are spent in the ground. The imago is reddish brown, marked above 

 with obscure whitish stripes on account of which Harris styled it "the scarred Melolon- 

 tha." Like tlie May beetle, it flies abundantly at dusk and during the evening. It dif- 

 fers from the various species of Phyllophaga, however, in the remarkable structure of its 

 antennae, the "club" of which is composed of seven broad ligulate plates or leaves. 

 These antennal plates have a much greater development in the male than in the female, 

 so that the sexes may be readily distinguished at a considerable distance. 



It is one of the most curious discoveries of recent investigators into the physics of en- 

 tomology, that an exceedingly delicate auditory apparatus exists in the antennae of many 

 insects. At the meeting of the National Academy of Sciences in November, 1873, Pro- 

 fessor A. M. Mayer described a series of experiments upon the antennae of the male mos- 

 quito. Placing one of these insects alive upon the stage of his microscope, he observed 

 the effects produced upon the numerous sensitive fibrillje with which the joints of the 

 antennae are provided. By bringing a vibrating tuning-fork into close proximity to the 

 mosquito, he observed that certain of the fibrillfe were thrown into rapid motion, while 

 the rest were comparatively motionless. Substituting a second tuning-fork, sounding a 

 different note, the first series of fibrillae remained motionless, while a second series was 

 thrown into rapid vibration. The experiment was continued with tuning-forks of still 

 other tones, with similar results. Professor Mayer thus made the discovery that the 

 fibrillffi of the mosquito's antennae are tuned by nature to vibrate in sets in unison with 

 sounds of different quality. 



In the antennal plates of Polyphylla variolosa no fibrilla; are present, but the surfaces of 

 these plates are furnished with innumerable minute vesicles, each of which is provided 

 with a nerve to communicate the vibrations received by the vesicle from the sounding- 

 body. 



The use of tlie antennae of the male mosquito is undoubtedly to guide him to his mate, 

 whom he must find in the dark. Pi-ofessor Mayer has shown that the song of the female 

 mosquito has the power of vibrating the fibrils of the antennse of the male in such a way 

 as to enable him to direct his flight in a straight line to the object of his search. In the 

 case of Polyphylla variolosa I believe that the male antennse have a similar function, and 

 that these organs in the genus have a development so far surpassing other genera of the 

 group to which it belongs, on account of the peculiarly difficult circumstances under 

 which the male discovers the whereabouts of the female. 



Two days after securing my first specimens of this beetle, at dusk July 15, 1874, I vis- 

 ited the same spot and found these insects so abundant that upwards of fifty specimens 



