ZOOLOGY AND UOl'ANY, MICUOSCOPY, KTC. 389 



Characters of Dipterous Larvae.* — John R. Malloch has done a 

 useful piece of work in studying- the larval and pupal characters of 

 North American Diptera, a synoptic account of which has been wanted 

 for a long time. Whac he has done (only Part I is published) will 

 enable students to identify many larval forms. The material is also 

 utilized in reference to the classification of the imagines. The author 

 presents a vast amount of information in effective form, and his 

 analytical keys are very valuable. 



Early Development of Horse Bot-fly. t — E. Roubaud discusses the 

 various theories as to the early chapters in the development of 

 Gastrophilus equi. Some say that the larvse hatched on the skin enter 

 the mouth and nostrils of themselves ; others say that they are licked 

 in by the horse's tongue ; and others that they penetrate the epidermis 

 and are ingested when the horse bites at its irritated skin. 



Roubaud's observations lead him to the following conclusions : — 

 1 . The eggs do not hatch spontaneously ; they may remain for some 

 weeks in a passive state on the skin. 2. The ripe egg liberates the 

 larva when touched ; licking is not essential. 3. The primary larvas, 

 liberated wdien touched with the mucous membrane of the lips or gums, 

 insinuate themselves horizontally below the epithelium. 4. The primary 

 larva3 do not perforate the skin ; their mouth-parts are not suited for 

 this. 5. The primary larva3 move and grow in the mucosa of the 

 mouth, working from near the surface to deeper parts. After the first 

 moult they leave the epithelium and pass down to the stomach. A 

 somewhat similar life-history seems to occur in Gyrostigma {Spathicera) 

 of the rhinoceros. As to the bots observed in cutaneous wrinkles in 

 man (rampant myasis), Rou])aud believes that the larvas enter by the 

 external mucous membrane of eyelids or lips, or by a cutaneous lesion. 

 They are not able to perforate the skin directly. 



Phylloxera Galls. |— Rosen finds that the leaf -gall produced on 

 Vitis vulpiiia by Phylloxera vastatrix begins on the bud leaves, and 

 produces a depression due to the upward growth of tissue at the sides. 

 There is no evidence of stimulus due to some chemical substance ; the 

 initial stimulus is the continuous sucking action of the insect at a single 

 fixed point. 



Pure Lines in Aphides. § — Ewing finds no summation effect of 

 selection in reference to six fluctuations of Aphis arenas. The fluctu- 

 ations do not seem to be germinal. Changes in body-length were found 



* Bull. Illinois State Lab. Nat. Hist., xii. (1917) pp. 161-109 (30 pis.). 



t Comptes Rendus, clxiv. (1917) pp. 453-6. 



X Amer. Jouru. Bot., iii. (1916) pp. 337-60. See also Trans. Amer. Micr. See, 

 XXXV. (1916) pp. 258-9. 



§ Biol. Bulletiu, xxxi. (1916) pp. 53-112. See also Trans. Amer. Micr. Soc, 

 XXXV. (1916) pp. 256-7. 



