of the Oil Beetle, Meloe, and of the Strepsiptera. 339 



closes the embryo is tensely stretched, the segments of the thorax of the 

 future larva, as well as those of the abdomen, are distinctly marked, and 

 traces of an alimentary canal are easily distinguished, although the whole 

 interior of the body is still composed of cells. In the last stage of the em- 

 bryo (fig. 32), immediately before rupturing its envelopes, the ovum measures 

 about one-eightieth of an inch in its long diameter. The embryo is now 

 completely formed. The whole of its abdominal segments, as well as its 

 thoracic, have their armature of marginal spines. The minute head of the 

 embryo, flattened, acute and wedge-shaped, projects forwards from the pro- 

 thorax, and pressing against one portion of the envelopes whilst the caudal 

 extremity is forced, by the growth of the body itself, in an opposite direction, 

 the ovum is made to assume an irregular ellipsoid form, and by a continua- 

 tion of the forces of growth the membranes and shell are at length burst, and 

 the young Stylops comes forth in the oviduct of its parent as an active hexa- 

 pod. The whole of these changes take place in the ovum within the body of 

 the female Stylops, herself contained within that of the bee. 



I regret that I was unable to obtain other specimens of Stylops for dissec- 

 tion at the period when the larvae have burst their envelopes. Enough how- 

 ever is shown in these observations to prove, with Dr. Siebold, that the female 

 Stylops is viviparous ; and also, that the eggs do not all become matured at 

 precisely the same period, but that there is a range of some days between the 

 hatching of the earliest and of those which appear last. That this is the fact, 

 was proved to my satisfaction in observations made on another stylopized 

 specimen oi Jndrena. 



On the 27th of May, only a few days after receiving the specimen which 

 contained these embryos, Mr. Smith favoured me with the loan of a stylopized 

 Andrena Trimmerana, which he had also captured at Hampstead about the 

 8th or 10th of that month, and which had been in his possession alive during 

 the intervening sixteen or eighteen days. The bee died on the 25th of May, and 

 on the same day one or two specimens oi Stylops larvae made their appearance. 

 On the following day many more came forth ; and soon after the bee was placed 

 in my hands they issued from the vaginal fissure (fig.20,c) of the Stylops in such 

 abundance, that they completely covered the whole of the posterior part of the 

 abdomen of the bee, both on the upper and under surfaces, like dust, which 



VOL. XX. 2 y 



