630 



TNSECTA. 



Pelecocera, Hoff., is unknown to me, but is at once distinguished from all with the antennae shorter than the 

 head, by the short, thick seta of the antennae. 



The sucker of all the other Athericirae is only composed of two setae, of which the upper represents 

 the labrum, and the lower the tongue. 



These Athericerae form three small tribes, which correspond with the genera CEstrus and Conops 

 of Linnaeus, and with that of Musca of Fabricius, as at first proposed by him. 



As Stomoxys and Ducentes are connected with the last of these genera, we shall commence with the 

 tribe CEstrides, Latreille, which is composed of the genus 



CEstrus, Linn., — 

 Well characterised by possessing, in the place of a mouth, only three tubercles, or but slight rudiments 

 of a proboscis and palpi. 



These insects have the appearance of large meat-flies, very hairy, their hairs being generally coloured 

 in rings, like Humble-bees. Their antennae are very short, each inserted in an excavation below the 

 forehead, and terminated by a rounded palette, bearing on its back, near the base, a simple seta ; the 

 wings are generally apart ; the alulets large, and hiding the balancers ; the tarsi are terminated by two 

 ungues, and two pul villi. 



These insects are found but rarely in the perfect state, the time of their appearance being very 

 limited. As they deposit their eggs on the bodies of various herbivorous quadrupeds, it is in woods 

 and pastures frequented by these animals that they are to be sought after. Each species of CEstrus is 

 ordinarily parasitic upon a single mammiferous animal, selecting, as the situation for its eggs, that part 

 of the body which is best fitted for the larvae, which either remain in that particular situation, or are 

 passed from thence to a more favourable place of developement. The Ox, Horse, Ass, Rein-deer, Stag, 

 Antelope, Camel, Sheep, and Hare, are the only quadrupeds hitherto known to be subject to the 

 presence of the larvae of CEstri. These animals appear to have a strange dread of the insect, when it 

 seeks to lay its eggs upon them. 



The nature of the abode of these larva? is of three kinds, which may be distinguished as cutaneous, 

 cervical, or gastric, according as they reside either in tumours formed in the skin, or in some parts of 

 the head or stomach of the animal destined to support them. The eggs, whence the larvae of the first 

 kind are hatched, are placed by the parent fly beneath the skin [of oxen, &c], which it [is stated by 

 some authors, including Latreille, but evidently erroneously,] to pierce with its ovipositor, composed of 

 four tubes, entering into one another, and armed at the tip with two hooks, and two other pieces ; this 

 instrument is formed of the terminal segments of the abdomen. These larvae, called taons by the 

 French peasantry [and luorbles or wornils by the English], have no need to change their situation, 

 finding themselves, as soon as born [or rather as soon as they have buried beneath the skin], in the 

 midst of a purulent humour, which serves them for nourishment. The eggs of the other species are 

 merely stuck upon various parts of the body, either close to natural and internal cavities, into which 

 the larvae easily penetrate, and there fix themselves, or where the animal is in the habit of licking itself, 

 whereby the larvae are carried by the tongue into the mouth, and so pass to the place [in the stomach] 

 destined to receive them. It is thus that the Sheep Bot-fly places its eggs at the inner edge of the 

 nostrils of that quadruped, which becomes agitated, stamps the ground with its fore feet, and hurries 

 away with its head to the ground ; the larva insinuates itself into the maxillary and frontal sinuses, 

 and fixes itself to the internal membrane with which they are lined, by means of two strong hooks 

 with which its mouth is armed. It is thus, also, that the Horse Bot-fly deposits its eggs, without 

 settling, by hovering in the air at intervals over the inner part of the legs, at the sides of the shoulders, 

 and sometimes on the withers. CEstrus hcemorrhoidalis, the larva of which also lives in the stomach of 

 the Horse, places its eggs upon the lips ; the larvae, attaching themselves to the tongue, pass by the 

 oesophagus into the stomach, where they subsist on the humour secreted by its inner membrane. They 

 are generally found round the pylorus, and rarely in the intestines. They often exist in great numbers, 

 hanging like a bunch of grapes : Mr. Clark, nevertheless, considers that they are rather serviceable than 

 otherwise to the Horse. 



These larvae have, in general, a conical form, and are destitute of legs. Their body is composed of 

 eleven segments, exclusive of the head, furnished with small tubercles and spines, often arranged in 

 bands, and which facilitate their progression. The principal organs of respiration are situated in a 



