jRetrospective Criticism* 301 



son may be sucked out by applying the anus of a hen to the part after scari- 

 fication ; or else a plaster of garlick, onions, and Venice treacle ; drinking 

 French wine, garlick broth, and taking mithridate, bezoar mineral, and 

 myrrh, &c." 



It will be hence seen the high estimation our forefathers had of the use of 

 the viper, and the mode of making some of its various preparations ; and 

 the great confidence they placed in its virtues in eradicating those now 

 unknown diseases (or, perhaps, better known by more intelligible names). 

 But thanks to the march of intellect, and the persevering researches of our 

 modern physicians, for the erasement of this and numerous other noisome 

 remedies from their present mode of practice. I am, Sir, yours, &c. — 

 D. N. Worksop, Sept., 1831. 



Parasites (Microgdster glomerdtus) upon the Cabbage Caterpillars. — The 

 calculation of Mr. Bree (p. 107.) upon the wonderful destruction of the 

 caterpillars effected by these little creatures (what between the sparrows 

 and the microgasters, the caterpillars seem to have a sad hfe of it), the 

 announcement of J. D., p. 109. (I have observed some curious facts con- 

 firming J. D.'s statement), that the perfect flies have not a determinate 

 time for appearing, and the statement of my friend Newman (p. 109.), 

 respecting the structure of the larva, are very interesting. I cannot, how- 

 ever, bring myself to concur in the supposition of the latter gentleman, that 

 the parasitic larvae derive their nourishment through the long, transparent, 

 hair-like appendage to the end of the abdomen, first observed by him ; and 

 for this simple reason, namely, that the larvae of the /chneumonidae are 

 furnished with the same organs of nutrition as are possessed by all the 

 other hymenopterous worm-like larvae. It is true that these organs are 

 very minute; they have not, however, escaped the delineator of your 

 figure 40 6, p. 108., although he has mistaken them for the tail instead of 

 the mouth of the grub. May not the appendage mentioned by Mr. New- 

 man have been one of the skins of the larva not entirely cast off? His 

 observation, that they entirely divested themselves of it before forming 

 their cocoons, confirms my supposition. In answer to Mr.Bree's questions, 

 at the foot of p. 106., I should imagine, from what I have seen of these 

 parasites, that each species is attached to its peculiar caterpillar ; hence I 

 do not agree with Mr. Newman in thinking that the Microgaster which 

 attacks the garden tiger moth (A'rctia Caja) is the same species as that 

 which preys upon caterpillars of the cabbage butterfly (Pontia brassicae) : 

 the question, however, requires close investigation. I will say nothing 

 at present upon the " relation of affinity, as the cant term expresses it," 

 which Mr. Newman considers may be established by this discovery between 

 Stylops and Microgaster. — t/. O. West wood. January 28. 1832. 



Humming in the Air. (p. 110.) — I would refer O. to Mr. Rennie's Insect 

 MiscellanicSy p. 89., and if he has not that work, I recommend him to pro- 

 cure it as soon as possible ; in the mean time I extract the following, 

 which 1 think will explain the " humming " to him. After quoting the 

 passage in White's Miscellaneous OhservationSy referred to by O., Mr. 

 Rennie proceeds : — " We have frequently observed this humming in the 

 neighbourhood of London, and for some time were as much puzzled to 

 explain it as White, till we, on several occasions, remarked a troop of 

 swallows hawking high overhead, where the humming was heard; there 

 could be no doubt, therefore, that it was occasioned by insects invisible 

 to us, on account of their distance." Mr. Knapp says thus, " that this sound 

 proceeds from a collection of winged insects, or bees, there can be no 

 doubt." Kirby and Spence (Introd. to Ent. ii. 377.) seem inclined to 

 refer it to insects of the order Coleoptera. — M. P. Jan. 12. 1832. 



Humming in the Air (p. 110.). — As corroborating O.'s conjecture, I 

 would refer you to an account transmitted to you last year by Mr. Jenyns, 

 of an extraordinary swarm of minute flies, which settled in the Lodge of 



