The Philippine Journal of Science 



19U 



taken place. Unfertilized females apparently do not lay. Sol- 

 itary females were kept from four to sixteen days in the labo- 

 ratory without copulation and laid no eggs, while those that were 

 allowed to copulate oviposited the first day afterwards. Egg- 

 laying extends over a period of from six to eight days, gradually 

 decreasing to the end. The maximum number of eggs is laid 

 within three days after copulation. 



The period of incubation of the egg varies greatly in the 

 Philippines. Certain eggs have been observed to hatch within 

 four days, while others kept under identical conditions took 

 ten. There may be a variation of three days in the time required 

 to hatch eggs laid by the same beetle on the same day. The 

 average time required is six days. The following table shows 

 the average length of the egg stage and the variation in hatching, 

 from May to November, 1911 : 



Table I. — Variation in incubation period of Lasioderma serricorne Fabr.' 



Date laid. 



1911. 



May 12 



May 14 



May IB __.. 



May 17 



May 18 _. 



May 18 _.. 



May 21 



July 28 



July 29 and 30 



Augrust 6 



August 7 



August 10 and 11 .- 



August 22 



August 26 



August 28 



August 30 



August 31 



September 1 and 2. 



September 28 



November 19 



Average . 



Hatchings. 



First. Second. Third. Fourth 



May 20 

 May 20 

 May 20 

 May 25 

 May 25 

 May 23 

 May 27 

 Aug. 5 

 Aug. 4 

 Aug. 11 

 Aug. 12 

 Aug. 17 

 Aug. 26 

 Aug. 31 

 Sept. 2 

 Sept. 

 Sept. 

 Sept. 

 Oct. 



Nov. 23 



May 21 

 May 21 



May 24 



Aug. 7 

 Aug. 5 

 Aug. 12 



Aug. 18 

 Aug. 28 

 Sept. 2 

 Sept. 4 

 Sept. 4 

 Sept. 5 

 Sept. 7 



Nov. 24 



May 22 

 May 22 



Aug. 6 



Aug. 19 

 Aug. 30 



Sept. 6 

 Sept. 6 



Nov. 25 



Aug. 20 

 Aug. 31 



Sept. 7 

 Sept. 7 



Variation 



in hatch 



ing. 



Days. 

 

 2 

 2 

 

 

 1 

 

 2 

 2 

 1 

 

 8 

 4 

 2 

 2 

 4 

 3 

 1 

 

 2 



2.2 



Average 

 period of 

 incu- 

 bation. 



Days. 

 8 

 7 

 6 

 8 

 7 



5.6 

 S 



6.6 

 6 



5.6 

 5 

 8 

 7 

 6 

 6 



5.6 

 5.5 

 5 

 4 

 5.5 



6.1 



■ The eggs used in these tests were laid by different individuals, but were kept under the 

 same conditions, and the record shows all eggs that hatched. 



The percentage of eggs that do not hatch is very small. Ex- 

 periments were conducted with 313 eggs, and of these only 14 

 failed, giving an average of 4.47 per cent. 



