Mr. F. Smith on Wasps and their Habits. 391 



whose habits we were not previously acquainted. Stizus 

 grandis, we learn, provisions its nest with Cicada septemdecem ; 

 Pepsis formosa preys upon Mygale Hentzii, and Chlorion cce- 

 ruleum upon spiders. 



A great mystery presents itself to Mr. Walsh : one or two 

 suggestions relative to its solution are thrown out, but no 

 opinion expressed. The insects included in the genus Pelo- 

 pceus, popularly known by the name of " mud-daubers," have 

 the femora and tibise almost destitute of spines or bristles ; 

 still some species (P. lunatus being an instance) have a few on 

 the tibias, principally on the underside of the anterior pair : 

 they are not, as Mr. Walsh remarks, so bristly as in the genera 

 Sphex and Ammophila, both burro wers in the earth ; but why 

 should they be so when the bristles are of no manner of use 

 to her, any more than they would be to a true wasp ? One 

 school of philosophers, Mr. Walsh observes, " will reply that 

 its legs are bristly because, ages and ages ago, in the dim far- 

 away vista of bygone geological years, the genus took its 

 gradual origin from some species that did really dig holes in 

 the ground, and had bristly legs to do so — and that, in con- 

 sequence of the disuse of its bristles for generation after gene- 

 ration, through myriads of geological ages, the bristles them- 

 selves have gradually become shorter, weaker, and less nume- 

 rous."- 



I would draw attention to one or two circumstances. I first 

 observe that Pehpceus is just as destitute of spines as we find 

 many other insects that are either known to be external 

 builders, or that construct their mud cells in ready-made bur- 

 rows or in some convenient hole or fissure adapted to their 

 requirements : such insects belong to the genera Agenia, Pem- 

 pkredon, Pison } and some others. 



But I shall perhaps add still further to the mystery when I 

 refer to the habits of one of the commonest species of our 

 sand-wasps, Mellinus arvensis, which is quite as destitute of 

 bristles on the legs as any species of Pelopoaits, and yet is a 

 true burrowing sand-wasp. There are hosts of insects with 

 spiny legs that never burrow into any kind of substance — 

 Diptera, for instance ; many species of blowflies are examples. 

 Spines are of use for other purposes than digging ; bees comb 

 and clean themselves with their spiny tibite and tarsi, as well 

 as free themselves from the thin pellicle in which they are 

 enveloped in the pupa state. I have witnessed the operation 

 of escaping from the shroud that envelops the pupa of Ammo- 

 phila sabulosa ; and here the use of the bristles becomes very 

 apparent. 



Mr. Walsh is not aware that what he considers to be his 



20* 



