ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
173 
placed on the caudal margin of the eleventh segment. Tlje tooth-horned 
fish-fly (Chauliodes rastricornis) belongs to a genus which has been little 
studied in the United States. The larvae live in rude cells gnawed out 
of soft hark and wood ; they ordinarily move by crawling along weeds, 
hut, when alarmed, can swim rapidly % suddenly doubling the body up, 
bringing the head in contact with the abdomen. They have also a 
peculiar habit of walking on the surface of the water, body downward, 
and can thus move along quite rapidly. When handled the larvae 
occasionally eject from the mouth a considerable quantity of a blackish 
fluid. 
The most important element of food for the lesser water -bug (Zaitlia 
Jluminea) appears to be the larvae and nymphs of dragon-flies ; the undu- 
lating back-swimmer (Notonecta undulata) lives mostly on May-fly 
larvae ; they appear to have the power of ejecting a poison into their 
victims, as the author twice found that the insertion of their beaks into 
his skin produced a j^ain very much like that of a bee-sting. The 
aquatic beetle, Donacia suhtilis, evidently plays an important role in 
effecting the pollenization of Nuphar advena ; it is interesting to note 
that Muller found that a congeneric species in Europe aids in the 
pollenization of the European representative of the American yellow 
pond-lily. The thirteen-spotted ladybird was found to have a decided 
preference for aquatic plants. The paper concludes with some notes on 
the eggs of the giant water-bug {Belostoma americanum of Leidy or 
Benacus griseus of Say). Technical descriptions of larvae, pupae, and 
imagines are in many cases given. 
Dorsal Gland in Abdomen of Periplaneta and its Allies.* — Mr. E. 
A. Minchin, who recently described j" a pair of glands lying between 
the fifth and sixth abdominal terga of Periplaneta orientalis, has since 
dissected other allied species, in which he has found interesting 
variations of this organ. P. americana does not, so far, differ from 
P. orientalis ; in P. decorata the glandular pouches are a little shallower 
and of greater lateral extent, and there is an additional gland which 
extends forward into the body-cavity ; this gland and its ducts are pro- 
liferations of the hypodermis, and there is no invagination of the cuticle. 
Blatta germanica exhibits the greatest complication of structure, though 
the female seems to have no trace of the organ. In the male it is 
relatively of enormous size, projecting far into the bodj-cavity, and 
being quite visible externally. The sixth tergum is much larger than 
those in front of it, and has two very large oval depressions of con- 
siderable depth ; each of these is further divided into two by a transverse 
ridge. The seventh tergum is still larger than the sixth, and emar- 
ginate in the middle line posteriorly ; just under the projecting edge 
of the sixth tergum there is a large median opening, divided into two by 
a median longitudinal septum ; these openings lead into large tubular 
invaginations of the cuticle and hypodermis. All the depressions and 
invaginations are lined by a tough brown cuticle of some thickness. 
Two kinds of hairs are jn-esent ; some are stiff, straight, and pointed, 
and are of the kind found all over the body ; others are very minute, 
short, and fine sensory hairs, which appear to be confined to the ridges 
* Zool. Anzeig., xiii. (1800) pp. 41-4. f See this Journal, 1889, p. 204. 
