MIGRATION AND DISPERSAL OF INSECTS : COLEOPTERA. 317 



(2) L. [{meridionalis x vibiiyni) x {meridionalis X viburni)] 3 X L. 

 [qiiercm (Dorset) X meridionalis] $ [= ^ (6 x 6) X $(5x2)]. 



Of this last about 30 ova were deposited, all sterile. The 

 above facts, while showing the sterility of the $ s, does not, of course, 

 prove that the (? s would be unable to fertilise other females. Whether 

 the sterility is due to the malformation of the female sexual organs, 

 or to some other cause I cannot say. All the $ specimens of this 

 cross seem, as far as one can judge externally, well developed. 



There is a possible cause of infertility which I do not remember 

 ever to have seen suggested which might be worth investigating by an 

 expert, though I have no evidence to show that it occurs. It was 

 suggested to me by the fact that the ova of the Paris querchs were 

 particularly large, though the moths themselves were, if anything, 

 small. If the differences in the ova extend to construction as well as 

 to size merely, it may be that (taking first the case of different species) 

 the particular shape of the orifices in the unimpregnated ovum, offer 

 some obstacle to the passage of the spermatozoa. In the case of cross- 

 breeds this might occur also on the hypothesis that, though the ovum 

 of either pure bred parent was permeable by the spermatozoa of the(? 

 parent, yet the combination ovum of the hybrid failed to possess the 

 essential characters of either. Take a rough illustration to make my 

 meaning clear. Suppose species A with a straight narrow orifice, B 

 with a bent wide orifice, either of which are permeable. The resulting 

 A X B might have an orifice both bent and narrow, which would form 

 an obstacle to entrance. This hypothesis is not put forward otherwise 

 than argumentatively, and I should be sorry to hold the opinion, without 

 any proof, but the subject of the sterility of hybrids being still 

 obscure, it is possible that the suggestion may be of use. 



(5) The only remaining cross into which sictda does not enter is : — L. 

 {meridionalis xribi(rni) 3' xqnerciis (Dorset) ? ( = 6x5). — Larvse of this 

 were obtained by Mr. Bacot from ova laid July 10th, 1897. No moths 

 were reared. 



{To be co7icluded.) 



Migration and Dispersal of Insects : Coleoptera. 



By J. W. TUTT, F.E.S. 



In 1867 the Melbourne papers reported enormous swarms of beetles 

 of a dark bronze colour, as occurring in Victoria. In the early part of 

 January, a swarm was noticed near Ararat, Victoria, flying in a 

 column about 20 yards broad, and keeping in compact order. They 

 cast a dark shadoAV on the ground, and they were about an hour in 

 passing the spot from which they were seen. At a certain point they 

 turned off' at right angles. The Eucalyptus trees in the neighbourhood of 

 these insects had been stripped of every particle of foliage. Great num- 

 bers of the beetles fell to the ground durnig the flight. The noise they 

 made while flying was said to be like that of a hurricane playing in the 

 rigging of a ship {Yorkshire Post, March BOth, 1867). A remarkable 

 flight of Lachnosterna tristis is recorded by Linton {Insect Life, i., p. 

 17), as passing from north to south over Burrows, in Indiana, on the 

 evening of May 7th, 1887 ; they flew in swarms or droves about one to 

 every 18 inches square, and from 5ft. to 12ft. or 15ft. above the ground, 

 the swarm being some one and a half miles wide ; when first seen, they 



