8054 



Insects. 



already known. I am perhaps wrong in using the term " facts " for 

 matters not yet positively proved, but I think the general evidence so 

 strong in favour of the conclusion I have formed as to leave little doubt 

 of its being correct. 



Any entomologist who has looked, even in the most casual manner, 

 at Gillmeister's valuable monograph on the Trichopterygidae, can 

 hardly fail to have noticed the great analogy between the three winged 

 Ptinelke figured on one side of pi. 324 (Sturm's 4 Deutschland's Fauna'), 

 and the three apterous species on the opposite side of the same plate, 

 and this resemblance is rendered more remarkable by the circumstance 

 that at the time the 6 Monograph 1 was published no other species of 

 Ptinella had been discovered. For my own part I always had an idea 

 that there were in reality but three species, of which the corresponding 

 winged and apterous individuals were respectively the sexes. And 

 although my subsequent observations have not to its full extent verified 

 this idea, yet quite enough has been discovered to prove that the wings 

 form a sexual mark rather than a specific distinction. Of one species 

 alone, P. ratisbonensis, I have before me more than five hundred 

 examples. Of this multitude about one-fifth exhibit black wings con- 

 spicuously developed, although varying in size ; in above two hundred 

 others the wings may still be seen through the transparent elytra, but 

 much diminished in bulk, and of a pale colour ; the remainder on a 

 superficial examination present no appearance at all of wings, but 

 when dissected are found to possess those limbs in a rudimentary state. 

 The variation in the size and colour of the wings is not occasioned by 

 the more or less matured condition of the individual, since specimens 

 recently hatched and in a soft state are found both with and without 

 coloured wings. It is therefore evident in this case that no specific 

 distinction can be formed on the apparent absence or presence of the 

 wings. Again, the colour of the eyes and the depressions on the disk 

 of the thorax are equally uncertain as marks of difference. In the 

 immense series now before me the colour of the eyes varies in different 

 individuals from a deep black to an orange of the same shade as the 

 other parts of the head, so that it becomes difficult to tell whether there 

 are any eyes at all. The depressions on the thorax are even more 

 variable. A few of my specimens, and but a few, have two placed 

 near the base of the thorax ; in others these depressions are connected 

 together, still occupying the same position ; in others, again, there are 

 two or more placed near the middle of the thorax ; while by far the 

 greater part have the thorax unmarked by depressions in any part. 

 And here I must observe that in many of Gillmeister's figures the 



