ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
171 
have anal hooks. Pro-legs are sometimes found on the lower surface of 
the first thoracic, and of the last abdominal segments, but those of the 
former are often more or less fused. In Simulium they are completely 
fused and have the form of a cone, while the posterior pair is reduced to 
two feeble projections with a large number of microscopic hooks. 
The respiratory apparatus varies greatly in the extent to which it 
is developed. In some genera there are two large longitudinal trunks 
which extend through the whole of the body of the larva and end by 
two open stigmata, while in other genera the apparatus is quite closed. 
The long trunks are divided into pieces which correspond to the seg- 
ments of the body ; in Mochlonyx the trunks keep their septa as a 
“ souvenir de leur anastomose.” Eight or nine pairs of solid lateral 
cords, ordinarily very delicate, pass from the epidermis to the longi- 
tudinal trunks. The trachem are at first full of serum, but later on 
become filled with air. When the tracheae are renewed alter ecdysis 
the old tubes are expelled to the exterior with a little air by the lateral 
cords, while the new tracheae, which may be entirely filled with serum, 
have the serum only gradually driven out by the air in the body. 
The trumpet-shaped organs of the nymph are at first filled with 
serum, but whether they have clefts or other openings, or whether they 
are closed, they become filled with air by the body. They are essen- 
tially hydrostatic organs or air-reservoirs, which serve to facilitate the 
last metamorphosis. The abdomen of the nymph ends in a pair of wide 
swimming-j^lates, and the last segment is wide and deeply incised ; and 
this segment can scarcely be said to be a true respiratory organ. 
The author concludes that the respiratory apparatus of Insects 
cannot be considered as a pure and simple formation of the epidermis, 
nor as resulting merely from the invagination of this layer. The con- 
nective tissue takes a more or less large part in the formation of tlie 
apparatus. In the larvee here described the lateral cords essentially 
represent invaginations of the epidermis. 
TJgimyia-Larva.^— Dr. F. Meinert gives an account of his own 
observations on the life-history of this larva, which imbeds itself in the 
Silkworm. He agrees with Prof. Sasaki, whose paper on the subject we 
noticed some time since, | in thinking that the eggs of the Ugimyia find 
their way into the body of the silkworm through its mouth, and he 
thinks it likely that other caterpillars are infested in the same way. 
The Ugimyia-maggot is only for a time located immediately inside one 
of the stigmata of the silkworm, and certainly does not form its bed 
“ by heaping up fats and muscular fibres,” for the bed is a widening or 
swelling of the trachea itself. This fact is fully in accordance with 
what is known of the parasitic life of many TacJiina-lsLVYse. The plates 
of the spiracles or stigmata of the parasitic larva are quite closed, as is 
the case also in other Musca- and CEstrus-lsivyse, with the exception only 
of Gastrojyliilus. 
New Cattle-pest.J — Mr. S. W. Williston has some remarks on a new 
cattle-pest in the United States which has been found on the horns of 
* Ann. aud Mag. Nat. Hist., v. (1890) pp. 103-12. 
t This Journal, 1887, p. 579. 
X Amer. Natural., xxiii. (1889) pp. 581;-90 (1 pi.). 
