FORFICULA AURTCULARIA. 45 



/aria, Dr. T. A. Chapman found that the nymph 

 passed through six moults, and therefore that there 

 were seven instars (not including the egg-stage), the 

 imago being the seventh. In the 1st instar the 

 antennas had 8 segments, in the 2nd and 3rd 10, in 

 the 4th and 5th 11, in the 6th 12, and in the 7th 

 (imaginal) 14. In two cases at the 3rd instar the 

 mother was dead or eaten, either having been killed 

 by her offspring or having died of old age. 



VARIATION AND ABERRATION. --F. nn'ri<'nl<tria may be 

 said, for an earwig, to show much variation, and this 

 takes place mainly along three lines : 1 , colour ; 2, mag- 

 nitude ; 3, shape and relative size of the callipers. 

 The colour may be so much darker than the normal 

 as to appear almost black, the legs also partaking in 

 the deeper tint. The difference in size is often very 

 striking even when there is no variation from the 

 usual form. For example Col. J. "W. Yerbury gave 

 me a male of the typical form taken at Spey Bridge 

 on 31 July 1911, whose total length was 20'5 mm., 

 5'5 mm. being clue to the callipers. On the other 

 hand I have a male from near Oxford whose total 

 length does not reach 12 mm. 



Usually, however, the large males have highly 

 developed and lengthened callipers. As mentioned 

 already, the names media, borealis, and forcipata were 

 given to these forms when they were thought to be 

 distinct species. It is necessary, however, to retain 

 forcipata only, which belongs to the extreme and 

 fairly constant form (fig. 2, no. 2), for intermediates 

 do not seem to occur at all frequently. Some of these 

 examples of var. forcipata are indeed fine insects. 

 One was taken, on 26 July 1910 by Percy M. Bright 

 on the cliffs at Freshwater in the Isle of Wight, 

 whose length from mouth to tip of callipers was 25 

 mm., the callipers themselves measuring 10 mm.* 



* It was evident on examination that the insect was damaged. When 

 etherised two dipterous larvse, each measuring 6'25 mm. in length, belonging 

 to the Muscidae, emerged from it. 



