154 [December, 3 



and only a fluid — a secretion — and not rather a portion of the 

 substance of the animal itself ? The larvae of G. raphani ar€ 

 furnished with similar latero-dorsal tubercles, of which the four or I 

 the meso- and metathorax are the largest. On the upper surface oil 

 these a minute puckered pore may be observed. But, although I have! 

 been breeding these larvae for years, it is only recently and accidentally I 

 I have discovered that under peculiar circumstances (circumstances.! 

 however, reproducible at pleasure) the larva emits from these tubercles! 

 a double row of clear liquid-like (stalked ? and) capitate protrusions.! 

 which, coming and going simultaneously, instantly brought to mind} 

 the figure in K. & S. on plate xviii. The conditions requisite for 

 evoking this phenomenon in the case of G. raphani, are exposure to 

 strong sunshine in a close moist atmosphere. The larvae may then be 

 observed as with a row of glass bead-headed pins stuck in on either] 

 side. But, at the least disturbance, these instantly disappear, so that 

 I could not touch them to see whether they were fluid or not. They! 

 do not seem to be accompanied with any smell. It was only afterwards, J 

 under different circumstances, I was able to arrive, with tolerable! 

 certainty, at the conclusion that these bead-like processes from the! 

 Gastropliysa larva are not a liquid secretion, but an everted portion of! 

 the insect itself, rather comparable to the horns of certain caterpillars. 1 



In what I call a double batch of between 80 and 90 eggs laid 

 (August 26th) by a $ which, having been originally kept as a virgin, 

 and which in that state laid some parthenogenetic eggs, was afterwards! 

 allowed to become impregnated, but became so only to an imperfect 

 extent, — in this batch, along with some perfectly healthy larvae, I found I 

 many that perished in the hatching, and among these several in which 

 these protrusions from the four thoracic tubercles were very striking. 

 They were quite analogous to those observed in the older larvae, and 

 were emitted from the same parts, viz., the pores of the latero-dorsal 

 tubercles of the thorax, the only part out of the shell ; and as they, 

 were no longer spherical, but elongate finger-shaped, and as they per- 

 sisted for many hours — in fact, were never withdrawn, during which 

 time they exhibited lateral twitching movements, I could not doubt I 

 their non-fluid nature. And this has suggested to me, that in the 

 case of Lina populi also, the main portion of the extrusion underlying 

 the milky, opaque, odorous fluid, may be an analogous solid portion of 

 the animal itself. 



Milford, Co. Donegal : 



October, 1880. 



