Séance du 16 Avril 1921 
139 
were obtained from egg-cases laid by N° 3 , of the 169 
adults obtained from paired daughters, 88 were fe¬ 
males and 71 males. This slight inferiority in the 
number of males in both generations may be quite 
accidental and due to our own selection of only a few 
young from each of many egg-cases. 
The 1 5 adults obtained from unfertilized egg-cases 
were all females. This number is too small to enable 
us to state that no males would be bred if longer series 
were taken. Nevertheless other considerations make it 
highly probable that males would only occur rarely if 
at all. First there is the important fact that only half 
the potential number of eggs hatch even in the very 
best cases; this seems to indicate that the other half 
cannot develop unless fertilized and, as the sexes occur 
in nearly equal numbers under normal conditions, 
we are justified in assuming until proof to the con¬ 
trary is forthcoming that only one sex — in this case 
the female — can develop from unfertilized eggs. Then 
we have the well-known fact that several species of 
the allied family, the Pliasmidae, reproduce normal¬ 
ly parthenogenetically, the males being extraordinarily 
rare; except for a few not quite certain cases, all the 
young so produced are females and several generations 
may be bred without the intervention of a male. In 
another family of the Orthoptera, not so closely allied, 
I mean the Acridiidae, Plotnikov (1921) p. 9, has ob¬ 
served parthenogenesis in several species; only one 
larva reached the last larval stage, but in all cases 
only females were obtained. 
