176 Descriptions and Figures of two Insects 



cles. This cannot, therefore, be the chrysalis of the turnip 

 insect, neither can it be that of the ichneumon of the barley. 

 Analogy teaches us that the gall-like protuberances upon the 

 turnips are the results of the attacks of a cynipideous insect, 

 and that the insect inhabiting this chrysalis cannot be the 

 cause of it. What, then, is this dipterous insect ? In the 

 absence of direct information, I conceive that Mr. Farmer 

 must have fallen into a mistake; that the chrysalis, instead of 

 being that of the turnip insect, was found within the sheath of 

 the barley ; that the injury sustained by the latter plant was 

 inflicted by the larva of this dipterous insect; and that the 

 larva of the ichneumon, instead of being the " anguis in 

 herba" [the snake in the grass], w r as parasitic upon the real 

 enemy. We know, indeed, that some of the Muscidae (Tephri- 

 tis, &c.) form galls upon plants; but here we have a real gall 

 fly caught in the act, while I am not aware that any of the 

 gall flies (Cynipidae) form cocoons; nor that any of the ich- 

 neumonidae are herbivorous. In fact, this is not the first mis- 

 take which has occurred of a similar nature, among those 

 who have not paid much minute attention to the ways of na- 

 ture. How often has the ladybird been regarded as the 

 cause of mischief to plants, when it has only abounded in 

 order to keep in check the myriads of plant lice (A'phides) 

 upon which its larvae feed ! How often has the tomtit bee \ 

 charged with the ravages of our gardens, when it has bee^ 

 busied only in thinning the swarms of noxious caterpillars or 

 other insects ! 



But there are other causes which induce me to fear that 

 this chrysalis is the real cause of the injury to the barley, since 

 two species of Muscidae have been ascertained to attack it. 

 Musca hordei Bierkander, and Musca frit Linnceus ; which 

 latter insect, although stated, by Messrs. Kirby and Spence, 

 not to be an inhabitant of Britain, is so similar, in its habits of 

 getting into the ear, to Mr. Farmer's account of his insect, 

 that I should conceive that the latter must be identical with 

 it; and, according to Linnaeus, the Musca frit annually 

 destroys a tenth part of the produce of this grain in Sweden. 

 The gelatinous larva of a Tenthredo (most probably a Cephus) 

 has, also, been ascertained to feed upon the upper surface of 

 the leaves of barley, so as to occasion them to wither. 



Mr. Farmer's turnip insect (Jig, 17. e,f) is a species of my 

 genus Eucoila, described in VI. 494. note *, having thir- 

 teen joints in the antennae of the female, which are thickened 

 at the tips ; a scutellum with three impressions, the basal 

 joint of the abdomen short and woolly, and the wings desti- 

 tute of a minute central submarginal cell. It is of a black 



