60 



[Miirch, 



But tlie question arises : How has this beeu brought about ? 

 Now there is a well known law that when an organ is not used, in 

 time it degenerates and is eventually lost. And just as there are 

 amongst ourselves the restless, roving individuals — the great mass in 

 these days of the race, and the quiet stays- at-home, so is it much the 

 same in the insect world. There are the active species tliat love 

 getting on the wing, and there are the sedentary stays-at-home which 

 never stir far from the spot where they saw the light. And here, 

 I may observe in passing, that this latter quality or instinct is, I 

 believe, one of the chief causes of the rarity or localness of those 

 insects which the collector delights to go in search of. 



Let me give the most striking instance that I know of, of this 

 stay-at-home habit. Many years ago the late Mr. Machiu captured in 

 the London district a few specimens of Goleophora inulas, an insect 

 which had never before been talcen in this countiy. Although he 

 visited the spot in subsequent years, he never again succeeded in 

 meeting with it, and the insect remained unrecorded, until I turned it up 

 here in Herefordshire. I found it occupying a corner, scarcely larger 

 than the table I am writing at, of a small drained pond. Here I 

 continued to find it for upwards of 14 or 15 years, and might be doing 

 so still, had not the pond been once more dammed up for the exigencies 

 of hop washing. Outside this tiny locality I never siicceeded in finding 

 it, althougli tlie food i^liint, I /nil a dyt>e liter ica, is very common in the 

 district, and even grew in plenty within 50 yards of the insect's home. 

 We must therefore recognise the stay-at-home instinct as a very potent 

 feature in some insects. 



Sometimes it seems forced upon them by the conditions under 

 which they live. And for an example let me turn to the Dipt era. 

 In the Plioridx, a family I have given some attention to lately, are 

 certain species (unfortunately we do not appear to have any of them 

 in this coimtry) which inhabit ants' and white ants' nests. The males 

 are scarcely known, and the only one thd^t is has functional wings ; 

 but the females have lost theirs, either com])letely or nearly so. In 

 the narrow passages of the ant's nest wings could not be used, and as 

 the nests are usually of a very permanent nature, the female insect, 

 with lodging for herself and food for her offspring all round her, is 

 under no temptation to leave and fly abroad in search of other 

 quarters. A still more interesting instance, because it shows the 

 steps of the process, is given by tlie new species PJiilijgria i^etnialata, 

 described and illustrated by Mr. Collin in the January number of the 



