MUSCIX.E. 23 



tubercles are smooth, and there are no prominent tubercles outlining 

 the stigmal field. The prothoracic spiracles have only a few lobes. 



Musca domestica L. 

 (Plate I, figt^. 1-4, 16.) 



The larva of the house fly has been described by several authors, 

 and very full}' by Dr. Hewitt. Tlie body is slender and tajiering in 

 front; large and truncate behind. The head has a tiny j)ai)illa each 

 side and there is but one great hook, apparently the union of the pair 

 seen in other forms. The prothoracic spiracles show six or seven 

 lobes; on the ventral base of the sixth and following segments there 

 is a transverse, fusiform, swollen area provided with minute teeth. 

 The anal area is but slightly prominent and shows two approximate 

 processes. The stigmal area is barely if at all concave and not out- 

 hned by tubercles; the spiracles are prominent, loss than their 

 diameter apart, each with three sinuous slits, and a button at the 

 base. In some cases two of the winding slits are apparently con- 

 nected. The second stage has but two straight slits in each stigmal 

 plate, while in the first larval stage there are two smaller slits on a 

 tubercle each side of the middle, and in this stage there are no pro- 

 thoracic spiracles. 



The larva of the house fly is rarely swallowed, but there are rec- 

 ords to that effect, and it sometimes breeds in decaying fruits and 

 vegetables. 



Psettdopi/relNa coniicina F'ab. 



-to* 



(Plate I. fio-s. 11-15.) 



Body rather slender in front, l)road and truncate behind. Head 

 from above distinctly bilobed, each with a distinct papilla; one large 

 mandible or hook. Anterior spiracle ,six or seven lobed. Surface 

 generally smooth at junction of segments; there are on sides usually a 

 few short, longitudinal tubercles or strise. Beginning with the sixth 

 segment each has on the ventral base a transverse, swollen, fusiform 

 area or pad which is provided with two rows of tubercles or longitu- 

 dinal teeth. Each ventral segment also shows a transverse groove 

 before the middle. The penultimate segment has a fusiform area 

 at aj)ex below with tubercles upon it. The last segment has the anal 

 area not very protuberant, above is a slender median ])rocess, and 

 at each side a larger, slender, lateral process; from them a row of 

 small teeth extends upward and toward base. The posterior stigmal 

 plates are large, close together, and each has the three winding slits 

 characteristic of the true Muscida\ 



The specimens were taken from cow dung, whicli Jiarhored lavvae 

 of Lyperosia irritnns L. 



