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 minutes.^ 

 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^ 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. 



PROPORTION 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. If, however, we omit records of 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 any egg-laying 



aBul. 60, Bur. Ent., U. S. Dept. Agr., p. 158, 1906. 



& Records based on a recording thermometer in the room with the eggs. 



