ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 551 



Stimulation of Hatching.* — Messrs. Severin and Hartung have 

 tried to discover the stimuli which determine the hatching of the eggs 

 of Chaetogsedia monUcola, a Tachinid Dipteron. The eggs are laid on 

 various grasses and weeds, and at the time of oviposition contain full- 

 grown larvse. The larva is a parasite in certain insects, e.g. caterpillars, 

 which eat the vegetation on which the eggs occur. The problem is to 

 account for the sudden hatching in the digestive tract of the host which 

 permits the parasite to begin penetrating the wall before being expelled 

 with the excreta. It seems that the digestive juices of the host, 

 reaching the larva through the micropyle, stimulate it to perform the 

 body- movements by which escape from the chorion is effected. 



Ichneumonid Parasite of the Plum-weevil.f — E. A. Cushman 

 describes the life-history of the ichneumonid Thersilochus conotracheli 

 Riley, a very abundant and effective parasite of the plum-weevil, 

 Conotrachelio nenuphar Herbst, the only insect which it is known to 

 attack. It is single-brooded, reaches the adult stage in the autumn, 

 and leaves its cocoon late in the following spring or early in the 

 summer, the males beginning to appear a few days before the females. 

 Parasitization takes place while the Curculio or weevil larva is very 

 small, and before it burrows into the fruit beyond the reach of the 

 parasite's ovipositor. The female thrusts her ovipositor into the tunnel 

 made by the Curculio larva, and piercing the skin deposits within it a 

 single egg. The larval parasite spends most of its time in its host, 

 leaving it when nearly full-grown, and draining the last trace of fluid 

 from without. It moults four times before leaving its host and 

 constructing its cocoon, which is oval, and made of tough reddish- 

 brown silk. Pupation takes place in four or five days after its 

 construction, and the adult stage is reached about the end of August, 

 the ichneumonid hibernating within the cocoon. The egg is oblong- 

 oval, about 0"33 mm. in length, and under a magnification of 

 215 diameters does not show any sculpture of the chorion. 



Life-history of Blow-fly and House-fly. | — "Winifred H. Saunders 

 has observed the egg-laying, etc., in the Bluebottle {Galliphora erythro- 

 cephala), the Greenbottle {LucUia csesar), and the House-Fly (Miisca 

 domestica). In the Bluebottle, eggs laid on September lst-2nd 

 hatched on 2nd-3rd ; the larvae pupated on 14-1 5th ; the flies emerged 

 on the 27th. For the Greenbottle the corresponding dates were 

 August 24th, 25th, September 4-5th, 15-29th. The Blow-flies lay 

 their eggs parallel with one another in compact groups ; the long 

 sensitive ovipositor feels the surface before the passage of each egg. 

 In hatching the egg splits longitudinally along a suture marked by a 

 white line. No moults of the larvte were discovered. 



The eggs of the house-flies studied were laid on bananas, either in 

 cracks or crevices of the pulp or under the loose skin. The maggots 



* Psyche, xxii. (1915) pp. 132-7. See also Trans. Amer. Micr. Soc, xxxv. (1916) 

 pp. 69-70. 



t Journ. Agric. Research (Washington), vi. (1916) pp. 847-56 (1 pi.). 

 X Proc. Zool. Soc. London, 1916, pp. 461-3. 



