Insects. 7885 



the abdomen were not dotted. On a careful examination wiili a microscope, which I 

 look into the garden, the ihread appeared only slightly thicker than an ungummed 

 line, but after a very short time undulations appeared, and subsequently, ai the most 

 regular distances, the viscid matter formed into aliernaling large and small globules. 

 The wliole process is such a beautiful illustration of molecular attraction, which Mr. 

 Rainey has been so patiently and iirofouudly working out with regard to the highest 

 organic structures, that I thought ibis simple example might interest some of our 

 members. The cold weather has, of course, driven away this spider till next autumn 

 at least, but the same result can easily be obtained artificially. — Richard Beck, in 

 ' Journal of Microscopical Science.^ 



Manffold IVicrzel Cmps injured hij a Species of Anlhomyia. — With a view to ascer- 

 tain the origin of the evil, I paid frequent visits to a mangold field, in order to 

 discover the fly which was the parent of the leaf- mining larva; whose existence within 

 the cuticles an intelligent farmer had first pointed out to me. I searched himdteds of 

 leaves, iu order to obtain possession of some pupae, but in vain. I brought home 

 several leaves containing full-grown larv«, which I anticipated would soon become 

 pupa;, and placed them in water, in hopes of thus being able to secure a pupa or two ; 

 but I found the larvap. always dropped out of the leaves. Failing in this, I determined 

 to watch the insects in the tield,and my suspicions were soon fixed upon a two-winged 

 fly with reddish brown eves, which was very abundant on the mangold leaves, and 

 seemed evidently to have some object iu view beyond tlie mere oidiuary and incidental 

 one of bCltliug upon them. I observed, on the under surface of the leaves, a number of 

 small white cylindrical ova, in clusters varying from two to six or eight together. On 

 holding these up to the light I could clearly see from the track, which extended from 

 the nii)tured ova between the cuticles to the larvce in another part of the leaf, that 

 these were the undoubted ova of the damaging insect; but it still remained to 

 prove that the suspected fly was the parent of tlie ova. I therefore made a micro- 

 scopical examination of the eggs which had been deposited on the leaves ; these, under 

 a power of 250 diauieters, presented a beautiful reticulated structure. I then dissected 

 a number of the flies, whose abdomens were evidently distended with ova, with a view 

 to compare the eggs in the ovary with tlnise I had already examined. I found them 

 iu every stage of development, and discovered some of the exact shape and size, though 

 of softer consistency than the eggs on the leaves, and presenting the same network 

 structure, characteristic of those which had beeu naturally excluded. About this time 

 I was made aiquainted with Jlr. Curiis's description of llie male Anthumyia Betae, 

 which exactly agreed with speciiuens I had taken myself, and as I afterwards discovered 

 a couple of flies in coilu I could no longer have any doubt on the subject. It appears 

 singular that this is the first instance on record of the mangolds suflermg to any extent 

 from the depredations of these larvae, the direct cause of the injury last year being the 

 large prupurtion ol female flies compared with tbe number of the males, being on an 

 aierage as twelve to one: from the fact of the males only being hitherto recognised, 

 there can be little doubt that iu former years this sex predominated, hence the immu- 

 nity of the piauts_^frum injuiy up to this time; but, as to the cause, whether atmo- 

 spheric or otherwise, of the large proportion of females during the last ye:ir, this is a 

 question which perhaps can never be scdved. The female fly continues to deposit ova 

 quite late in the season ; I found this to be the case as late as the fir.-t week iu 

 November. I cannot think that the lar»CB change to pupie in situ; I never could 

 delect a single pupa iu the leaf, and ray observations, so far as they go, tend rather to 



