No. 431.) MICROCOSM OF THE DRIFT LINE. 857 
ORDER OF SUCCESSION. 
These insects do not come all at once, nor “hit or miss," 
but follow a fairly regular order of succession. It was seldom 
that the same form was dominant at two visits. Between 
April 14 and 21 very few insects were found, and no regular 
record was kept. The temperature was cool and the winds 
variable during that period. On April 25, after four days of S., 
S.W., and W. winds, followed by E. and S.E. winds, more forms 
appeared. Two days of strong (thirty to forty miles per hour) 
W. wind, followed by a S.E. wind, brought in a few forms on 


















WIND PREVIOUS TO COLL. T Temp. F. SPECIES. 
Bow Dav or Corr. 
Days. Direction. Av. Vel.|Direction.| Av. Vel. | Max. | Min. | New. | Old. | Total. 
| 
Apr. 25 2 W.to E. 19 S.E. 14 69 42 IO | I II 
28 | 2 W: 374 S.E. 15 61 48 | 3 | o 3 
May 2 2 E. to N.E. 20 S.W. 18 82 53 37 5 42 
12 3. |N.E.toE.to N.E| 21% N.E. 10 56 43 27 10 37 
16 7 N.E. t E. 16$ E. 10 61 48 | 6 19 25 
23 2 S.W. to S. 12] S. E. 10 77 6r | 13 19 32 
27 2 W. to N.W. 15 NES 18 50 40 8 7 15 
a 3 S.W. 17) S.E. 15 75 60 | 2 14 16 





(Data kindly furnished by the U.S. Weather Bureau, Chicago, Ill.) 
April 28. All this time the temperature was cool, only once 
rising over 69° F. On May 2 a N.E. wind (twenty miles), 
preceded by a W. wind, brought in a good many forms, thirty- 
seven new species being found, besides several previously col- 
lected ; the rising temperature (53°-82°) probably influenced 
the numbers. On May 12 twenty-five new species were 
found, besides an abundance of old ones. This rich supply 
was probably due to three days of W. and S.W. wind, fol- 
lowed by four days of N.E. and E. wind (averaging eighteen 
and three-fourths miles) which continued until May 16 with 
decreased velocity (thirteen and one-fourth miles), the tem- 
perature never exceeding 61? F. On this day only five new 
