OF WASHINGTON. 149 



these plates in Margarodes are chitine. He stated that, in his 

 opinion, the larval exuviaB form a small proportion of the shell, 

 as he had not been able to find, upon close microscopic examina 

 tion, in any one shell more than two of the scales which showed 

 the larval rostrum. 



In reply Professor Riley said that the last speaker must remem- 

 member that all Coccid secretions are not wax ; that even in 

 Vinsonia the glass-like lateral secretion is of very different char 

 acter from the dorsal waxy tuft. Mr. Uhler emphasized this 

 point, and spoke of the varying character of Coccid secretions. 

 Mr. Hubbard said further that in the empty shells small frag 

 ments of chitine, trapezoidal in form, and 30 to 40 in number, 

 are found. This fact he considers very significant in connection 

 with the formation of the shell. Dr. Stiles considered it essen- 

 to cross-section the shells, but said that this would be very diffi 

 cult to do. He advised a combination of the Whitman wax 

 method with the Heider gum-mastic method, and offered to per 

 form the sectioning if specimens were given him for that pur 

 pose. 



Mr. Hopkins read a paper entitled : 



NOTES ON THE HABITS OF CERTAIN MYCETOPHILIDS, 

 WITH DESCRIPTIONS OF EPIDAPUS SCABIEI, SP. NOV. 



By A. D. HOPKINS, 

 (Entomologist, West Virginia Experiment Station). 



The rearing of Epidapus and of species of Sciara from scabby 

 and diseased potato tubers, in 1891, led me to undertake some 

 investigations for the purpose of determining the relation of this 

 class of insects to the so-called potato-scab. Some of the facts 

 so far obtained will, I trust, be of sufficient scientific interest to 

 present to this Society as a contribution to the knowledge of the 

 somewhat neglected family Mycetophilidae. 



The authorities Osten Sacken, Schiner, Winnertz, and others, 

 refer to Mycetophilids, or fungus-gnats, as a class or family of 

 insects the larvaB of which inhabit and feed upon fungi, decom 

 posing vegetable matter, animal manures, and like substances. 

 In a recent work, entitled "An Account of British Flies," by 

 Theobald (Vol. i, 1892, p. 105), the author says : " If, as men 

 tioned in a former page, they do a certain amount of damage to 

 mushrooms, the amount done is small compared with the benefits 



