138 



THE AMEEICAN ENTOMOLOGIST. 



tion, wallow in moist decaying matter, whether 

 animal or vegetable ; and as in such situations 

 they would be sometimes stifled for want of 

 air, if thej- breathed through the spiracles Or 

 breathing-holes with which all air-breathing 

 insects are supplied, nature has replaced the 

 spiracles by lateral "branchix" or gills, b)^ 

 means of which they are enabled, after the 

 fashion of a fish, to extract the air from the fluids 

 that suri'ound them. On referring- to our Fig- 

 ure 93, b, the reader will see at once the structure 

 of these curious gills, which, however, are by 

 no means peculiar to this genus of Insects, but 

 occur in a great number of larvas that iuhabit 

 the water, for example in those of the Mayflies 

 {^Ephemera family). These larvre dift'er further 

 from those of the true Flower-flies in the tail 

 end being much less conspicuously docked, and 

 in the body being considerably flattened, in- 

 stead of plumply rounded in the shape of an 

 elongate cone. It was probably in reference to 

 this peculiar flattening of the body of the larva, 

 that Bouche gave to the genus the distinctive 

 name of "Flat-fly" (Ilomalomyia) , fvom. two 

 Greek words which bear that meaning. 



In the perfect state — as sometimes happens 

 with closely allied genera — the Flat-flies do not 

 differ so materially in their structure and gen- 

 eral appearance from the true Flower-flies as 

 do the larvfe belonging respectively. to these 

 two genera. Still, as the larval habits of these 

 two genera differ so widely, and as the Flower- 

 flies, iu the original and more extensive signi- 

 flcation of the term, form a very extensive 

 group — authors having described no less thau 

 Go species of them as found in North America — 

 we must considei' the separation of this very 

 large and unwieldy genus into two smaller 

 genera as a judicious step. The minute details 

 wherein the Flat-flies difler from the Flower- 

 flies in the perfect fly state, as they would only 

 fatigue the general reader, will be found in the 

 foot-note.* 



We have ourselves bred what Baron Osteu 

 Sacken, to whom we have forwarded specimens, 

 thinks is in all probability a true Flat-fly, from 

 larvas very similar to those figured above, but 

 scarcely more than half as large (Ilomalomyia 

 prunivorci) . These larvae we met with in great 

 abundance in a mass of tame plums so much 



*Tlirough the kindness of JJavon Osten Sacken, "welearu 

 that Homalomijia is charaoterizeil by Schiner as having 

 inueh iiariviwer <;h''eks than Anthomyia, wlience the head is 

 more louiiilcd and iivejeel> le,>s On tlie nnderside of the eyes; 

 an(\ also Ii> tlu- abdomen Ijciiig less hairy. On comparing a 

 speeies a^' Homalomijia which, as will I'je stated hereafter, 

 M'e have ourselves bred from the larva, with Anthomyia 

 hrazsiciE, these generic distinctions ave ohvions, both the 

 legs and the abdomen in the latter being rather bristly than 

 hairy. 



decayed as to become almost semi-fluid. Tlie 

 fly produced from them is only about one-fifth 

 of an inch long ; whereas from the largest spe- 

 cimens sent us by Dr. "Wilson we might expect 

 to raise a fly at least one-third of an inch long. 

 If, therefore, there was no other reason than 

 this, we might be pretty sure that the two spe- 

 cies are distinct. But, as the scientific reader 

 will perceive from the descriptions given in the 

 foot-note, there are other reasons for believing 

 them to belong to separate species of Flat-flies.* 



*IIOMALO.vviA WiLSOxi.— La rua— Length when extended 

 0.37 inch; when contracted 0.28 inch, from 3| to 8 times as 

 long as wide. Color pale-brown, the sutures brown-black, 

 but only when the body is contracted . Head entirely retrac- 

 tile, wdth its anterior extremity slightly emarginate, and 

 with two minute black hooks on its inferior surface. Body 

 U-jointed, anil anal joint large and apparently composed of 

 two continent joints. The sutures in the contracted speci- 

 juens forming a strongly elevated carina both above and 

 below, but in those that are elongated forming the usual 

 impressed stria with a subobsolete carina in front of it. 

 .Toints 1— 3 capable of being much elongated when the head 

 is exserled. Joints 4—10 each with a i>air of lateral, trans- 

 versely-arranged, flesh}-, elongate-conical, bipectinate, 

 branchial processes, eacli process about one-tliird as long as 

 the body is wide, and the bipectinations, themselves a little 

 sprangling, basally about one-third as long as the iirocesses, 

 and gradually decreasing in length towards the tip of the 

 process. .Joints 1—:) with only one stich lateral process, 

 which is shorter and shorter as each joint a)»i)roaches the 

 head; the Uth or large anal joint wuth six such processes a 

 little longer than an}- of the rest, placed one behind another 

 at regular distances all round the lateral suture. .Joints 1 — 11 

 each witli a pair of small, transversely-arranged, dorsal, 

 tubercular branchia', which are slightly ciliated and about 

 as witle as high on joints 4 — 10, bid on 1 — 3 are more aud 

 more subobsolete, as each joint ai)proaches the head, while 

 on 11 they are twice as high as wide and twice as long as on 

 the preceding joints, and are placed on the anterior hall of 

 the joint exactly in range with the two anterior lateral pro- 

 cesses. Ventrallj' joints 4—10 are each furnished with 

 pseudopods, namely, two transverse rows of papillie; the 

 anterior row nearly attaining the lateral processes, and 

 having its papillse almost continent, so as to look like a 

 transverse carina; the posterior row shorter, less distinct, 

 and with jjapillas not contiguous. On joint 11 the posterior 

 row of ]iapilla! is replaced by the amis, which forms a vei-y 

 large elongate tubercle with an elongate impressed slit in it, 

 and has a small tubercle on each side of it. — Described from 

 4 contracted and 5 extended specimens, received, as stated 

 in the text, from Dr. Wilson of Quincy, to whom the species 

 is dedicated. 



HoMALOMYiA ruuxivOKA. — Larva — Differs from the above 

 only as follows: — 1st. The length when contracted is only 

 0. IS inch, and is^aboufc 3^ times as long as wide. 2nd. The 

 sutnres are not brown-black when the body is contracted. 

 3rd. The sutures are never carinate. 4th. The lateral 

 branchiae are fully hiilf as long as the body is wide, and the 

 hipectinations are subobsolete: as in WUsoni, those on the 

 thoracic joints are proportionally shorter. 5th. The dorsal 

 brauchifB, when contracted, are about 2-J times as long as 

 wide and blunt at tip ; but when extended are fully 4 times as 

 long as wide, trumpet-shaped, almost acute at tip, and closely 

 resembling the lateral branchiae, towards the base they are 

 slightly ciliate . As in Wilsoni^ those on the thoracic joints 

 are not so much developed, and those on the anal joint are 

 about one-lourth longer. 6th, The tw^o transverse rows of 

 papilliB (pseudopods) on ventral joints 4^10 are each of them 

 like the posterior row in WUsoni. 7th. The anus is rather 

 round th.an elongate. — Described from two specimens out of 

 a lot from which, as hinted in the text, were bred Aug. 25th — 

 Sept. 15th 7 c? 7 § imagines 0.18—0.23 inch long, both sexes 

 of a nearly uniform gray color except that the basal J or f of 

 the abdomen both above and below is of an obscure clay- 

 yellow in $ , aud in cj* is of a much brighter yellow with a 

 black dorsal line which is widely dilated before each suture. 

 Such sexual distinctions seem to be not unusual in this group 

 of flies; for Baron Osten Sacken infonns us that ' ' the sexes 

 in Anthomyia generally differ vei'y considerably in size and 

 colorings . 



HOMAiOMYiA Leidyi — lariia— .Judging from Dr. Leidy's 

 brief description of a larva which, as will be subsequently 

 stated in the text, was found on two occasions in the human 

 bowels, and which— as he has given it no name — we have 

 here for convenience sake designated as Leidyi^ is interme- 

 diate in its characters between WUsoni and prunviora. In 

 length it is said to be from 0.25 to 0.29 inch. The dorsal 

 branchia; seem to agi'ee generally with those of prunivora, 



