WERNER MARCHAND 81 



period of nearly nine full days. It has been proven that the eggs 

 of tabanids hatch more quickly when exposed to the sun during the 

 day (see Chrysops), where they are usually deposited; therefore the 

 time given is probably too long for eggs under natural conditions. 



There is no definite way, as far as our knowledge goes, according 

 to Hine, of telling the eggs of the black horse-fly from those of other 

 species of this genus, but being a large species the masses are much 

 larger than in some others, and are more convex than usual. The 

 particular place of oviposition is in a measure characteristic. 



It is of interest to note that the egg masses of Tabanus atratus are 

 often found to be parasitized. 



When the two egg masses mentioned and described by Hart had 

 produced larvae they were placed in a dry vial, and a little later it 

 became evident that both masses had been parasitized by Hymenop- 

 tera, minute black imagos emerging freely in the vial. An exami- 

 nation of one of the masses showed that about one-half of the eggs 

 had been infested. Examples of the imago were sent to Mr. W. H. 

 Ashmead, who found the species to be a new one. It was described 

 by him as Phanuriis tahanivorus (Ashmead). 



I give the description of this insect at the end of the chapter on 

 Tabanus, under the heading, Parisites of the early stages of Tabanidae. 

 The illustration of this insect, given by Hart, has been omitted. 



Hart is also the first to tell us about the early larval stages of 

 Tabanus atratus. From the two egg masses he obtained larv« 

 hatched as already stated, on August 4 and on August 18. In the 

 latter case, the incubation period was determined to be one week. 

 The larvae were at this time commonly found in water among the 

 vegetation, less commonly in the sand of the shore, and young indi- 

 viduals became frequent. 



Larva, Newly Hatched {According to Hart). — "In this stage the lateral areas 

 are sculptured similarly to those of the adult, but the dorsal and ventral areas, 

 though shining, are rather sparsely striated. Traces of the dark markings are 

 visible, especially on the posterior segments." 



According to Hine, the larvae, when first hatched, are about 3 mm. 

 in length, white, and with a narrow darker shade at the union of 

 each tv/o segments. As soon as they drop to the ground they begin 



