1881.] Larval Habits of Bee-FNes. 445 
vation will show that there is a still further parallel, in that the 
newly-hatched larve of the bee-flies are much more active than 
the later stages, and somewhat different in structure. 
The three later stages of the insect may be characterized as 
follows: | 
Larva (Pl, vi, Fig. 1)—We quote herewith our former de- 
scription: : 
“Average length, 0.50 inch. Body curved, glabrous, tapering 
posteriorly, swollen anteriorly. Color opaque whitish, with trans- 
lucent yellowish mottlings, and some venous marks at sutures, 
especially along medio-dorsum. Sutures deep. A lateral row of 
swellings, Head small, flattened, dark brown, in five pieces, con- 
sisting above of a frontal ovoid piece and two lateral pieces of 
somewhat similar form, and each bearing near tip a minute, two- 
jointed palpus; beneath of two broad, subtriangular jaws, having 
forward and lateral motion, and each, also, bearing near the cen- 
ter, in a depression, a two-jointed feeler. A spiracle each side in 
a fold between joints 2 and 3, and another on each side of the 
penultimate joint, 12. None otherwise perceptible.” 
ith additional material we have been enabled to examine 
Pus of these lower pieces when viewed from above is, as repre- 
sented in the figure (Pl. v1, Fig. 1 d), circular, with two dark 
marks indicating minute appendages. 
When the larva is fresh and plump it shows the greater swell- 
ing of the thoracic joints and the translucent mottlings mentioned 
vis years after a locust invasion might stand a much better chance of finding appro- 
Priate food, and of thus perpetuating the species. In this case and in most other 
cases of retarded development with which we are familiar, the exceptional retarda- 
_ Hon may and does become a benefit to the species, enabling it to bridge over periods 
of adversity. And we can see how, by the preservation of such favored individuals, 
the habit of irregular development may have become fixed in the species as a conse- 
quence of Surrounding conditions and circumstances which render it advantageous, 
