64 
Psyche 
[Mar. 
hazy-bright. There was still some fog lingering over the 
marsh at Conomo Point, Essex, when I arrived at nine- 
thirty. On approaching the Point, a sharp left turn was 
made over a small hut abrupt rise from which the road 
falls quickly away to the tide line. The first cottage on 
the left was surrounded on three sides by salt marsh. 
There was a convenient place to park in front of it. Im- 
mediately after getting out on the marsh a continuous low 
buzzing sound was noted. Then swarms of greenlieads 
were seen hovering just a few inches above tile dense 
cover of the fine marsh grass ( Spartina patens). On the 
far side of the cottage a slight depression was discovered 
where a small, sparse patch of the larger and coarser 
Spartina alterniflora stood. On the upper surface of the 
broader blades of these plants some mating pairs of 
greenheads were seen. One was resting on the back of 
the other with its head about over the mesothorax of the 
mate beneath. Although it was possible to approach the 
paired flies more closely than is usual with individuals, 
they remained alert and were not too easy to catch with 
the net. The carrier could still take off readily and fly 
rather well. If disturbed they would move to another 
plant two or three yards away while retaining their rela- 
tionship. Four or five pairs were caught there and they 
included the first males taken. Another stop was made 
at the same place on August sixth. In the thirty or forty 
minutes then spent on the marsh only five or six flies were 
seen. This time the owner of the cottage mentioned above 
was there. After explaining the purpose of the visit to 
him, Mr. Derby remarked that a carpenter he had engaged 
to work on the building in a previous year had told him of 
the hum produced by the hovering flies. This volunteered 
information was of interest in the light of my own experi- 
ence. That spot is apparently a regular mating place for 
this species. 
