100 



THE PRACTICAL ENTOMOLOGIST. 



The above may be considered as the normal life 

 of the Wheat Midge. Some individuals, however, 

 instead of going under ground, construct their 

 filmy cocoon in the ear of the wheat, where they 

 passed their larval existence, attaching it very 

 slightly, and usually at one end only, to the chaff 

 of the ear. This cocoon fits so closely to the body 

 of the larva that, being transparent, nothing can 

 be seen of it but the small portion of it that pro- 

 jects at one end beyond the body of the larva. In 

 this respect it agrees exactly with the cocoon of a 

 Willow Grallgnat, ( Cecidomyia s. hrassicoides), 

 which I have described, and of which I have 

 closely examined many hundred specimens; and no 

 naturalist, who compared the two together, could he- 

 sitate for one moment in pronouncing that the two 

 are of precisely similar nature. In both cases, if 

 the larva is allowed to remain undisturbed, it re- 

 mains within its cocoon ; but in the case of the 

 Wheat Midge, when the wheat is thrashed, or 

 when a few infected ears are rubbed out in the 

 hands, that portion of the cocoon by which it was 

 slightly attached to the chaff of the ear, some- 

 times becomes ruptured. Then, and then only, 

 the larva crawls out of its house, being apparently 

 unable to repair the damage to the old cocoon. 

 Many other insects will do the very same thing. 



Upon this slender foundation of facts, a mythical 

 theory was based by certain American authors, 

 namely, that it was the " skin" of the insect, and 

 not its cocoon, that under these circumstances it 

 crawled out of; and that it was the normal habit 

 of the larva to moult its " skin" in the ear of the 

 wheat, and then go under ground and pass into the 

 pupa state, without forming any cocoon whatever. 

 Whereas it is contrary to all entomological analogy, 

 that any larva should moult, after it is full fed, 

 until it gets ready for the final moult into the pupa 

 state; the various moultings of the larva being 

 only performed for the sake of allowing its body to 

 grow larger, and any larval moult after it is full 

 fed being utterly causeless and unnecessary. And, 

 moreover, it has since been clearly proved by Dr. 

 Fitch, that the larva of the Wheat Midge does 

 really, whenever it goes under ground to transform 

 into the pupa state, form a filmy cocoon iu the 

 manner described above. {N. Y. Rep. Ill, pp. 

 60-1). Hence it is but reasonable to infer that, if 

 the insect makes a cocoon when it goes under 

 ground, it will also make a cocoon in the compa- 

 ratively few and exceptional cases, when it stays 

 above ground and transforms in the ear of the 

 wheat. 



A few cases have been noticed in Europe, where 

 the larva of the Wheat Midge transforms into the 

 pupa state in the ear of the wheat the same season, 

 and comes out into the fly state the same season, 

 instead of lying dormant till the following summer. 

 I am not aware that any such cases have been ac- 

 tually oKserved by practical entomologists in this 

 country, but there is reason to think that in Ame- 

 rica, as well as in Europe, this occurs occasionally. 

 In the same manner most of the Canker-worm 

 moths come out iu March, but some few make 



their appoarance-the preceding autumn. And so 

 with many other insects. 



The practical inference to be drawn from our 

 examination into the Natural History of this in- 

 sect is, that whenever wheat known to be infested 

 by the Wheat Midge is thrashed and winnowed, 

 the " tailings" should always be either scalded or 

 burnt up. They will almost always be found to 

 contain a great number of the larvae of the Wheat 

 Midge, mo.st of them still enclosed in their tight- 

 fitting filmy cocoons ; and these, if allowed to live, 

 will probably produce Flies next June to re-stock 

 the farmer's wheat-fields with this destructive 

 pest. 



As to the specimens sent me from Pennsylvania 

 by Mr. llathvon, they were all, so far as I could 

 see, naked and without any enveloping cocoon, or 

 so-called "skin.'' I explain this fact in the fol- 

 lowing manner : The violent swash of the waters 

 broke up a certain percentage of the cocoons 

 that it disinterred, washing away the coating of 

 earth and rupturing the delicate membrane that 

 remained. Hereupon, as is their habit, the larvae 

 crawled out of their desolated houses, or were 

 washed out of them by the flood, and floating 

 above the heavier particles of earth carried along 

 by the water, formed an orange-colored scum on 

 the surface, after the waters subsided. On the 

 other hand, such cocoons as did not have the coat- 

 ing of earth washed away from them, would be apt 

 to settle down lower in the mud left by the flood ; 

 or even if they remained on the surface, would es- 

 cape notice on account of their being of the same 

 color as the mud. When the naked larva? revived 

 from their half drowned state, they naturally bur- 

 rowed under ground, by way of effort to attain 

 a position where they could safely pass into the 

 pupa state. I doubt very much whether nature 

 would enable them to form a new cocoon under 

 ground ; and in default of the natural protection 

 from excessive drought or excessive moisture af- 

 forded by that cocoon, I doubt also whether such 

 individuals will ever succeed in attaining the Ply 

 state. Possibly some few may do so, as the time 

 is but short which they will have to bridge over 

 between the Larva and the Fly state. But I do not 

 believe that many will. 



The reason, in all probability, why but very 

 few of these conspicuous orange colored larvae 

 were met with anywhere else in the field, ex- 

 cept in the hollow that had been flooded, and 

 on the higher portions none at all, is because 

 they were only visible to the eye when they 

 were washed out of their earth-colored cocoons by 

 the flood of waters. Dr. Fitch has remarked that 

 it is " almost impossible to discover these cocoons, 

 even with the aid of a magnifying glass, whore 

 they lie in their natural situation iu the ground of 

 old wheat-fields." {N. Y. Rep. Ill, p. 61.) Hence 

 it would be a very unsafe inference to arrive at, 

 that because the orange colored larv<e were only 

 seen by the farmer of Lancaster Co. in certain 

 portions of his field, therefore there were none in 

 the remaiuing portion, Mr. Bathvon tells me that 



