76 Psyche [April 



have observed it in other groups of insects, notably by Fabre on 

 Scarites gigas Fabricius (Coleoptera) ; by Holmes on Ranatra 

 sp. (Heteroptera) ; and by Rabaud and by Bohn on several 

 orders (Bouvier, 1919, pp. 79-89). In Macrosiphum the habit of 

 dropping to the ground and remaining motionless for a time is 

 e\Tidently a means of eluding a pm*suing enemy. 



Summary of Section IV. ^lany species of MacrosipMim 

 possess the habit of "death-feigning" when disturbed. 



2. The habit is exhibited by Macrosiphum tanaceti in all of 

 its stages, except in the first instar. 



T''. Parturition. At birth, the caudal portion of the nymph 

 appears first at the vaginal slit. The antennae are directed pos- 

 teriorly and closely appressed to the body walls. The legs and 

 cornicles are also in the same condition, the appendages thus 

 following the general contour of the body. The tarsi of the 

 metathoracic legs are in intimate contact with each other, 

 forming at the caudal portion of the abdomen a conspicuous 

 acutely subcorneal projection. The color of the nymph at birth 

 resembles that of the freshly molted nymph or adult. The body 

 and appendages are uniformly light apple-green and gloss}', and 

 the ej'es are reddish vermillion. The enveloping membrane 

 covering the young at birth, which has been described by Webster 

 and Phillips (1912) in Toxoptera graminum Rondani, by Baker 

 (1915) in Eriosoma lanigerum Hausman, and by other authors in 

 other species of aphids, has also been observed by me in Macro- 

 siphum tanaceti. The results of the present work agree with 

 Baker's account in that the envelope ruptures while the nj-mph 

 is partially extruded from the vaginal slit of the mother. The 

 nature of this membrane is still in question; although, from my 

 observations on M. tanaceti, I am led to beHeve that it probably 

 arises from the follicular epithelium, which persists to this stage 

 without degenerating. A more detailed discussion of this sub- 

 ject will be given in a later paper on aphid embryology which I 

 am publishing. If my observations, therefore, are correct, this 

 envelope is not a homologue of the vitelline membrane of the 

 eggs of amphigonous aphids, as Webster and Phillips have 



