363 
1916-17.] The Family Chermesidse. 
Gillette (37), Patch (47), and Crystal (31) have contributed to the 
knowledge of the North American species, while Stebbing (49, 50) has 
traced the biology of a spruce (Picea morinda ) — silver fir ( Abies webbiana) 
species. Patch (47) observed gallicolse of the abietis type settling entirely 
on spruce and there laying yellow eggs. 
Buckton’s (11) descriptions are untrustworthy. 
Burdon (13) reviewed Cholodkovsky’s first monograph, and has re- 
searched on methods of control for Chermes (12). Burdon’s work was 
very helpful in spreading a more accurate knowledge of this group in 
this country. 
From the above outline it will be seen that for the spruce-larch genera 
and species there are two main groups of questions yet to be finally settled : — 
A. Is the existence of the parthenogenetic species real ? If so, are there 
three species of the genus Chermes s. str. in Europe, namely, 
Chermes occidentalism Choi., Ch. abietis, Kalt., and Ch. viridis, 
Ratz. ? What are their life-histories and distribution in Europe ? 
B. What is the degree of complexity of the life- history of each 
species on the larch host ? 
4. Technique. 
The various workers have used varying methods in conducting their 
biological experiments. The aim of the author was to begin by ap- 
proximating the experiments as closely as possible to nature, and gradually 
evolving a more artificial and controlled system, when it was seen that 
such could be safely done. Thus in the introductory experiments here 
recorded interference was reduced to a minimum. 
Fundatrices and colonici, and later their progeny, were observed from 
birth. In selected cases egg-laying was observed under a binocular 
microscope, and the rate of egg-laying determined. The adult gallicolse 
were dealt with as follows : — 
A. Part allowed to remain on galled twig of spruce. 
B. Part transferred to clean spruce. 
C. Part transferred to clean larch. 
B showed the effect of disturbance, and eliminated the possible error due 
to that cause. The sexuparse w^ere transferred to clean spruce. In one 
half of the experiments the twig was sleeved before the winged stage was 
reached and after transference ; in the other half the insects were allowed 
freedom. In later experiments muslin cages were used. In the laboratory 
egg-clusters of colonici were placed separately in petri-dishes, and allowed 
