OF WASHINGTON, VOLUME XVII, 1915 121 



served, four belonged to Desmometopa m-atrum Meig., and two 

 to D. m-nigrum Zett. The spider was a full-grown female of Misu- 

 mena vatia Cl. At that time Lundstrom was not acquainted 

 with Biro's observations and had only read the article by Mik. 

 He therefore sought to determine more closety the possible re- 

 lation of Desmometopa to the bees. By catching bee after bee, 

 he satisfied himself that the flies do not travel with them. Freshly 

 killed bees pinned to the flower-heads of Cornus alba failed to 

 attract them, and bits of white paper with honey spread on them 

 also gave a negative result. Lundstrom concluded that Des- 

 mometopa associates with predaceous insects and "immediately 

 after eclosion from the pupa seeks a spider or predaceous insect, 

 to remain associated with it thenceforth and feeding only upon 

 the remains of its prey." In his opinion it is only in this manner 

 that the seeming rarity of these flies, abundant enough under 

 proper conditions, can be accounted for. 1 



Finally, C. A. Frost, in a short note, has indicated that in 

 America Desmometopa has similar habits, the species observed 

 by him (D. latipes Meig.) being indeed found in both hemispheres. 2 

 All these observations indicate that commensalism in Desmometopa 

 is a well fixed habit, furthermore showing some additional special- 

 ization in certain species. 



Under the head of "Notes and Exhibition of Specimens/' the 

 following were presented : 



MIGRATING ARMIES OF MYRIOPODS. 



BY H. S. BARBER, Bureau of Entomology. 



Just before dusk one day near the end of May, 1903, a sur- 

 prising migration of myriopods was observed by the writer, 

 the army issuing from the Redwood forest on one side of a logging 

 railroad at Fieldbrook (Buckman), Humboldt Co., Cal., cross- 

 ing the track on both sides of a little hollow spanned by a short 

 trestle and entering the woods on the other side of the cleared 

 right-of-way. The width of the marching army was perhaps 

 120 feet, and the width of the cleared right-of-way was about 

 200 feet. One could not walk in this area without crushing many 

 at each step and it was difficult to count the rapidly moving 



1 Lundstrom, Carl. Om Desmometopa-arternas snyltgastning hos 

 spindar och rofinsekter. Meddol. Soc. pro Fauna ct Flora fennica, Heft. 

 32, p. 100-104. 1906. 



2 Frost, C. A. Peculiar habits of small Diptera, Desmometopa lali JH * 

 Meig. Psyche, vol. 20, p. 37. 1913. 



