THE CONCHUELA. 37 
estimated at 7 hours and 55 minutes. It is a notable coincidence 
that in the case of the eggs of the spined soldier-bug {Podisus macu- 
liventris Say) the author found in Massachusetts that with an aver- 
age daily mean temperature ranging between 62° and 72°, 1 ° of tem- 
perature corresponded with approximately 7 hours and 40 minute-.'' 
An instance of a much more prolonged incubation period was not 
included in the foregoing table but was reserved for separate discus- 
sion, as it is evidently a case of intermittently arrested development, 
due to low temperatures. The egg batch in question numbered 28 
eggs and was deposited on October 17; 13 hatched on November 3. 
The average daily mean temperature 6 during the 16 days of incuba- 
tion was 65.7° F. The average daily maximum for this period was 
72.3° F. and the average daily minimum was 59° F. To the author 
it seems plain that the 16-day period can only be explained by 
the supposition that development of the eggs was arrested from time 
to time by the low temperatures. Here again a comparison with the 
records obtained from the eggs of the other species of the Pentatomid 
mentioned in the preceding paragraph is instructive as showing the 
adaptation of the physiological processes of the two species to climatic 
conditions. The eggs of the spined soldier-bug at Amherst, Mass., 
with practically the same average daily mean temperature (65.5° F.) 
hatched in 8^ days, or after a period one-half as long as in the case of 
the eggs of the conchuela. 
PROPORTIOX HATCHING IN THE LABORATORY. 
In many cases no note was made as to whether or not eggs hatched, 
but the records of nearly a thousand eggs will suffice to give fairly 
accurate knowledge on the subject. The eggs selected were deposited 
during July and August by conchuelas collected in the cotton fields at 
Tlahualilo and abnormal conditions were eliminated, as will be ex- 
plained. The total number of eggs was 942, and of these 68, or 7.2 
per cent, failed to hatch. Eggs of the conchuela deposited in the 
field seldom fail to hatch if not destroyed by parasites or predaceous 
enemies. The number of unparasitized egg-batches collected in the 
field is too small to permit the drawing of conclusions concerning the 
proportion that hatch, and for information on this point laboratory 
data, must be used. \(, however, we omit records o{ eggs from 
infertile females and of certain abnormal eggs, mechanically pre- 
vented from hatching, there is no reason to expect any appreciable 
difference in the proportion of eggs hatching under Laboratory con- 
ditions and those hatching under normal field conditions. Infertile 
eggs have never been collected in the field nor has anv egg-laving 
«Bul. <>(), Bur. Km., V. s. Dept. Agr., \k L58, L906. 
6 Records based on a recording thermometer in the room with th< 
