fn sects. 407 



pupa-cases ; but it struck me as so contrary to what obtains amongst 

 numerous species of insects possessing apparently less power of ex- 

 tricating themselves that I determined upon trying some experiments. 

 I collected pupae on several occasions, but they invariably perished ; 

 time after time I was disappointed- Last summer, having previously 

 well considered my plans, I collected a number of cocoons from the 

 nest of Formica rufa, and placed, first, a quantity of the materials of 

 which the nest was composed in a box ; then laying the cocoons 

 carefully upon this, I covered them with more of the materials of the 

 nest. At this time a few females and males were to be found deve- 

 loped in the nest. I placed the box in a warm but shaded situation, 

 covering it with gauze ; the following day I found two females had 

 made their escape, but were very inactive when I found them, and 

 soon died, probably for want of nourishment. I was obliged to leave 

 home, and neglected to give orders for the removal of the box, and 

 the afternoon's sun reaching it, all the rest of the ants perished. The 

 experiment, however, has satisfied me that ants can extricate them- 

 selves, although probably they are generally assisted by the neuters. 

 I intend following up the same course next season, and shall procure 

 a number of neuters, to whose care I shall give the individuals which 

 extricate themselves, should I again succeed in my experiment. 



There is another extraordinary circumstance connected with the 

 economy of ants, which has perplexed me not a little, namely, that I 

 sometimes find enclosed and naked pupae in the same nest, of some 

 of the species of the genus Formica. De Geer, as well as Latreille, 

 observed this fact ; I do not remember that Huber did. 1 have found 

 them in the nests of Formica fuliginosa, flava and fusca ; in Septem- 

 ber last I found a great number of the pupae of F. fusca under bark, 

 all naked, none were enclosed. I observed one female and but few 

 neuters. The pupae were lodged in shallow grooves, excavated in the 

 trunk of the tree : 1 brought home a number, and took some care in 

 my endeavours to rear them : only two individuals arrived at maturity. 

 I am inclined to believe that those larvae which do not spin have not 

 received sufficient nourishment ; and that like other insects not well 

 fed, they never arrive at the full perfection of the species. And it will 

 be remembered that all the pupae of the genus Formica which have 

 been observed naked, have been invariably neuters, or the least per- 

 fect sex, otherwise imperfect females. 



Humble-bees without wings. I once observed, like your correspon- 

 dent, Mr. Holme (Zool. 336), three or lour humble-bees, late in the 



