510 Scientific Proceedings, Royal Dublin Society. 



are induced to oviposit early, and a correspondingly early emergence of a 

 brood of adults will result. 



This early emergence further helps in the multiplication of the species, 

 because it is completed before the pulling of the ilax crop begins, and the 

 soft, delicate pupae in the soil will thereby escape possible injury and destruc- 

 tion during the process. The weather during the hibernating period and the 

 convenient presence of suitable and reliable winter quarters are also 

 factors which undoubtedly influence to a large extent ultimate infestation. 



The season of 1920 was particularly wet and cold, with little sun during 

 the early part of May. Egg-laying was consequently delayed, and the 

 emergence of the resulting brood of adults had only commenced when the 

 pulling of the flax crop started. The pupae were present in the soil in con- 

 siderable numbers, and no doubt many were destroyed, and others injured 

 sufficiently to prevent emergence of the adults. The mortality would be 

 further increased by the subsequent operations, such as carting, and further 

 by stock grazing on the fields after the flax had been removed. 



Besides these checks on emergence, the wet, cold soil must have caused a 

 comparatively high death-rate amongst the newly hatched larvae, as actually 

 occurred in the rearing experiments conducted in laboratory cages, when the 

 soil in which the supporting seedlings were grown was watered to excess. 



These adverse conditions may, therefore, have been responsible for the 

 singular freedom from attack last season (1921), and, if so, we may antici- 

 pate bad infestations during seasons following a dry and warm spring and 

 summer. In this connexion it is interesting to note that Carpenter, when 

 recording the unusually destructive attacks of May, 1912, states that such 

 were " probably as a result of the hot and dry summer of 1911 " (9). 



10. — Descriptions of the Immature Stages. 



(«) The Egg (PL XVI, fig. 6). — Elongate, oval in shape, cylindrical, 

 with rounded ends ; where two or more are pressed together in a cluster, the 

 sides sustaining the pressure are sometimes flattened. The chorion is tough, 

 and under high magnification is seen to be covered with numerous depres- 

 sions, which are bounded by more or less straight Hve-, six-, or seven-sided 

 walls, the raised areas between the depressions giving to the surface a 

 distinct and characteristic network appearance (PI. XVI, fig. 7). After 

 oviposition, the colour is pale yellow, and the surface appears shining and 

 translucent; during hatching the colour changes to yellow- brown or orange, 

 and the surface becomes opaque and dull. Eggs which have been deposited 

 for eight or nine days show up in fairly striking contrast to the soil in which 

 they are deposited. 



