48 SUMMARY OF CUERENT RESEARCHES RELATING TO 



of monovoitines. The eggs of monovoltines must hibernate if they are 

 to hatch out regularly ; those acclimatized in Madagascar hatch out very 

 regularly twelve to thirteen days after being laid, without any exposure 

 to cold, which is indeed injurious. The author describes a method 

 of dealing with the pairing methods and the eggs Avhich seems to 

 lessen the risk of pebrine. There is an indigenous silk-moth, Borocera 

 madagascariensis, which produces a coarse silk, and has quite different 

 habits. 



Variations in Silkworms.*— A. Lecaillon has inquired into the 

 characters of "bivoltine" variations which crop up accidentally in 

 normal races of Bombyx mori. In three sets of eggs showing " bivol- 

 tinism," there was so little yellow colouring matter that the eggs seemed 

 almost w'hite. There is some chemical peculiarity in the vitellus 

 distinguishing them from normal " univoltines." Daring embryonic 

 development, the colour-changes in the bivoltine eggs were quite 

 different from the usual succcosion, which is yellow, rose, reddish, dark 

 red, greyish, slatey-grey. Four days after laying a few of the pale 

 bivoltine eggs showed a faint rose ; on the fifth day a go.od many were 

 of this colour ; on the sixth day most of them had still their original 

 coloration. 



Past experience in reoring accidental bivoltine variations has been 

 very unsuccessful. They seemed to have little vitality or resisting power. 

 But Lecaillon has not confirmed this. He found them easy enough to 

 rear, and the mortality from disease was not greater than usual. There 

 was nothing peculiar in chrysalis or moth, in the pairing or in the 

 number of eggs laid. 



Parthenogenesis in Silk-Moths. f — A. Lecaillon finds that diverse 

 races or varieties of Bombyx differ in their liability to parthenogenetic 

 development. In some cases the parthenogenetic changes in the 'ig^ 

 may stop at a very early stage ; in others they result in a vigorous larva. 

 Actual cases are cited. 



Parthenogenesis in Otiorhynchus sulcatus.| — J. Feytaud finds 

 that this formidable vine-beetle is in general parther.ogejietic. Among^ 

 3000 he found no males ; he has never seen a male. Each female 

 produces about 150 eggs. Parthenogenesis is known to be the rule in 

 the allied species 0. tuna, 0. cribricollis, 0. Ugustki. 



Study of Myelophilus minor. § — Walter Ritchie gives an account of 

 the structure and habits of this beetle, rare in Britain, which attacks 

 pine plantations. It is contrasted in detail with the well-known M. 

 piniperda. The slight differences between the sexes of M. minor are 

 indicated. The brood galleries of M. minor are very characteristic, 

 and it is quite easy to distinguish them clearly from those of M. pini- 

 perda. The specificity of habit is very interesting. The reproductive 



* Comptes Rendus, clxv. (1917) pp. 683-5. 



t Comptes Rendus, clxv. (1917) pp. 799-801. 



t Comptes Rendus, clxv. (1917) pp. 767-9. 



§ Trans. R. Sec. Edinburgh, lii. (1917) pp. 223-3i (2 pis.). 



