( clxxvii ) 



size is undesirable in the Females, but that the size of the 

 Males is unimportant. 



Now as to the " marriage-flight." This is certainly not a 

 monopoly of these particular species. The phenomenon com- 

 monly known as a " marriage-flight " — the soaring together 

 of both sexes high into the air — has often been observed and 

 described, more especially in the case of social Hymenoptera 

 (e.g. Formica, Myrmica, etc. (Ants), Vespa (Wasps), Bomhus 

 and Apis (Bees), but we do not find that it involves in any 

 such case an increase of size in the ^. Take the Ants — the 

 (^(^ in some Genera, e.g. Formica, are about as large as 

 their ? $, but more often smaller — sometimes {e.g. in Lasius) 

 paradoxically so, and in no Genus (I believe) larger. Take 

 the Wasps and Bees — the $ is the larger sex both in Vespa 

 and Bomhus : of Apis I have already spoken. If it be 

 assumed that a " marriage-flight " like that of the Social 

 Aculeates is an absolute necessity to Myrmosa, Methoca, etc., 

 then, since the ? ? of these insects are apterous, great size 

 and strength might no doubt be an advantage to their $ $. 

 But (1) we have almost no evidence as to the details of pairing 

 in these comparatively rare insects ; (2) in many of the species 

 nearest to them the 5 ?> though apterous, are as large and 

 strong as their i^(^, and (3) a "marriage-flight" cannot be 

 necessary to Mutillidae as such, for in some of them both 

 sexes are apterous ! Again, in Anthidium there seems no 

 more reason why the $ $ should be specially adapted to carry 

 the $ 9 through the air, than in any of the Genera nearest to 

 it {Osmia, Megachile, etc.) where certainly no such adaptation 

 occurs, Anthidium $ ? are strong and rapid flyers, and if a 

 " flight " were necessary, they could quite well take their 

 share in it. But I even doubt if such a " flight " occurs at 

 all ! I have never seen anything like it, though I have often 

 seen Anthidium spp. pairing. The $ hovers in the air like 

 a Syrphid : the $ pounces on her, and the two generally come 

 tumbling into the herbage, and remain there (unless my 

 memory deceives me) till they part. There is absolutely, so 

 far as I know, nothing of so special and distinctive a character 

 about the pairing of Anthidium, as to necessitate a reversal of 

 the normal proportion in size between the sexes. 



M 2 



