56 Bulletin Wisconsin Natural History Society [Vol. 11, Nos. 1-2 
was seen towards evening over the University cane fruit garden, 
May 29, and again May 30. A rainy day and later a hard cold 
north wind inhibited much swarming from May 31 to June 4, 
tho thousands of these flies clung to the under side of leaves of 
bushes and trees, or in the grass, where also thousands of stone 
flies were keeping close to cover at 2 p.m. On June 4, there were 
great swarms flying, but a cold spell, June 5 to 6, checked them. 
June 7, 1912, still bigger swarms were seen, the temperature 
moderating slowly. 
CHANGE IN PREDOMINANT MIDGE SPECIES 
Though desultory collections were made, observations were not 
continued in earnest until June 12, despite that midges were 
present in the interim from June 7. On the 12th about ten 
kinds of midges were taken, and a few of the rarer forms on June 
14, 15 and 16. The lists of other sorts of insects increased greatly 
in this week and are therefore omitted, though the specimens are 
accessible at the Public Museum, Milwaukee, Wis. 
A trap lantern was arranged on the 17th, 18th and 19th with 
little success, only four of each of two common kinds of midges 
being taken. On the 20th there was less success but on the 21st 
I turned the trap directly towards the lake and secured three or 
four dozen Chironomids. Scattering collections were made on 
the 22d but on the 23d, midges were in still greater abundance. 
On the 29th and 30th, trap collecting was again good. July 1, 
the little black midge so common in the first month of collecting, 
had nearly disappeared from the swarms of the last three days, 
and was replaced by a black species with a shiny thorax, as the 
predominant type. 
SWARMING AND MATING 
On May 24 at 6 a.m., following the storm of the 23d, the proc- 
ess of mating was observed among several couples, tail to tail, 
the claspers of the slim male abdomen grasping tightly the stouter 
tipped female abdomen, pairs noted May 25, as also in copula, • 
suggest the period of fertility. 
In the evening of May 24, considerable time was spent watch- 
ing the increased swarms of the common early black midge noted 
