September, 1888.] 73 



NOTES ON PRAYS CURTISELLUS AND RUSTIC A. 

 BY T. A. CHAPMAN, M.D. 



It is now a good many years since Mr. Stainton decided, on what 

 he considered hardly sufficient evidence, that these two forms were 

 one species, and the matter has not since been conclusively worked 

 out. It so happens that during the past twelve months the oppor- 

 tunity has fallen in my way of making an extensive acquaintance with 

 both forms, and especially with rustica. I have no doubt both forms 

 are, as Mr. Stainton determined, but one species, and though this is a 

 less interesting result than the contrary would have been, my observa- 

 tions may be worth recording, as they disclose a hitherto unnoticed 

 chapter in the history of the species. 



Towards the end of June, 1887, I examined certain galls on some 

 ash trees, which I had often noticed in past years, without paying 

 them any attention. On two trees to which I had easy access these 

 galls were numerous, and I afterwards found not a few others in the 

 neighbourhood. The gall is a curious woody development of the 

 stalks of the inflorescence, which becomes aborted, with a rough 

 almost woolly surface, and of very irregular knotted shape ; in size 

 from about that of a pea to masses nearly as large as a fist, but usually 

 about the size of a small walnut. During the past few years these 

 galls have been very large and numerous on infected trees, and as they 

 persist for several years as dead woody masses, are often very con- 

 spicuous. This year I find they are not growing so well, and the 

 fruit is partially or wholly developed on them. It appears that these 

 galls are caused by a microscopic mite of glassy transparency, dis- 

 covered, as Mr. McLachlan informs me, by Dr. Low, and described by 

 him in a paper, " Ueber Milbengallen des Wiener-gegend," in the 

 24th Vol. (1874) of the Verb, zool.-bot. Ges. Wien, pp. 499—500. 



As I was not at the time aware that this fact had been demon- 

 strated, I was inclined (though of course in error) to attribute them 

 to one or other of two larvae that I found in them. One of these is 

 a small gall-midge (Diplosis sp.) with a rather active little yellow 

 larva, which is double brooded ; the larva passing the winter in its 

 cocoon. Mr. Meade tells me that the cocoons of these larvae are 

 supposed to be an exudation from the surface of the larva, but this is 

 certainly not the case with this species, as I have seen it actually 

 spinning its cocoon, which is of veritable silk. The cocoon is made in 

 any crevice of the gall, both by the summer and winter broods. 



The other larva was Lepidopterous, and, after sundry guesses, was 

 surmised to be that of Curtisellus, which in the event proved to be 

 correct. 



