110 Prof. E. W. MacBride and Miss A. Jackson. 



extraordinary statement that the male proceeds from a fertilised egg, whereas 

 the female is parthenogenetically produced. He kept a dozen larvaa in 

 darkness from hatching, and found that they began to turn dark about the 

 third moult. 



Schleip (1911) deals with the colour varieties of the adult insect and with 

 the changes in colour produced by variation in light. He classifies the 

 adult varieties of coloration into four types — (a) green, (b) green with 

 yellowish spots, (c) yellowish brown, and (d) brown. Of these types 

 (a) included half the individuals, (b) about a quarter, (c) about 5 per cent., 

 and (d) about a quarter. Examination of the ectoderm reveals the fact that 

 three distinct pigments are concerned in jDroducing the colour, viz., a green 

 pigment distributed in small grains throughout the cytoplasm of the cells, 

 a brown pigment distributed in large round grains in the base of each cell, 

 and a yellowish-red pigment distributed in angular masses near the centre of 

 the cell in the vicinity of the nucleus. In the green variety of insect there 

 is always a certain amount of brown pigment present. In the reddish and 

 brown varieties the green pigment is absent and is replaced by greyish dots. 

 Schleip maintains that the brown varieties become darker when kept in the 

 dark — contrary to the general rule for such changes, because melanic 

 pigmentation of all kinds when subject to change usually becomes lighter in 

 the dark. This increase in the darkness of brown individuals is due, 

 according to him, to the streaming of the brown pigment over the cell. The 

 brown pigment granules leave their basal position and stream over the cell. 



We may say at once that we have not been able to confirm these observa- 

 tions of Schleip ; but whether they are well founded or not they have no 

 bearing on the question of there being at least two well marked categories of 

 insects so far as relates to colour, viz., those with green pigment and those 

 without. It is obvious also that in the green category belong all those sub- 

 divisions which can be described as olive-green and green with spots. 



Methods Employed. 



Our preliminary experiments showed us that the insects reared from the 

 eggs with which we began our research were in all cases parthenogenetic 

 females. These when mature acquire a bright patch of scarlet coloration on 

 the inner sides of the femora of the forelegs and then begin to lay eggs. 

 Part of the original batch of eggs was given to the Insect Department of the 

 Natural History Museum, and amongst the insects raised by them one male 

 appeared. As the male is much smaller than the female and liable to be 

 confounded with an immature female, this discovery led us to discard the 

 results of our initial experiments, and to take especial precautions against 



