§ 355. THE INSECTA. 463 



abdomen.'^' This penis is composed of three articles with Aesdima, LiLel- 

 lula, and Gomphus ; but of one only with Calopteryz, and Agrio?i, with 

 which it is not directly adherent to the seminal vesicle. The male Libel- 

 lulidae are obliged, before copulation, to fill their vesicula seminrilis, which 

 is situated at the base of the abdomen. This they accompli.'^h by bending 

 the posterior extremity of the abdomen, so as to meet and empty the semen 

 into this vesicle. They then seize the female by the neck, by means of their 

 anal pincers, and she places her genital orifice in contact with the copula- 

 tory apparatus of the male,**^ These anal pincers of the males have very 

 distinct specific characteristics, while the females, on their part, have, in 

 the separate species, equally specific sculptured markings on the protho- 



rax. 



(?) 



With the Coleoptera, the copulatory organs consist of a more or less 

 horny sheath enveloped by a membranous prepuce, and containing a 

 broadly-flattened penis which consists of a canal supported by two lateral 

 horny ridges. At rest, these organs are entirelj' withdrawn into the abdum- 

 inal cavity, but can be widely protruded out of it by means of a very remark- 

 able muscular apparatus.*^' With the male individuals o? Dermestes, there 

 is a median orifice on the third and fourth abdominal segments, from which 

 projects a brush of stiff bristles connected with a round muscular body situ- 

 ated on the internal surface of each of these segments. This brush is un- 

 doubtedly some way connected with the act of copulation.^'-" 



§ 355. 



The development of the larvae of Insecta in the egg, occurs in the same 

 manner as with most of the other Arthropoda. After the unusually early dis- 

 appearance of the germinative vesicle,^'' there is formed, from a superficial 

 and partial segmentation, a round or oblong-oval blastoderma, whose 

 hyaline aspect contrasts with that of the rest of the vitellus.<-> This blas- 



S For the copulatory organs of the Libellulidae, 1 The germiuative vesicle is never observed ia 



see Ratlik<!, De Libellar. partibus genital., and my eggs that have been layed ; it has disappeared 



researches in Germar's Zeitsch. It. p. 421. even in tliose still in the oviduct ; this disappear- 



The act of copulation of the Libellulidae has ance would uot appear, therefore, to depend upon 



been represented by Swammerdamm, Bib. der the act of fecundation. 



Nat. Taf. XII. fig. 3 ; Reaumur, Mem. &c. VI. '-i Tlie first phases of the development of Insecta 



PI. XL. XLl. ; and Roesel, Insectenbelust. Th. have been studied by Herold (Disquisit. de Anim. 



II. Insect, atiuat. Class. II. Tab. X. vertebr. carent. in ovo format. 1835-38) witli 



r Tlie diffeivnt forms of these pin:ers have been Spinx ligustri and Musca tomitoria; and by 



figured in Charjientier, llova,e Entomol. Tab. I.. A 6//iA«r (Observ. de prima Insect. genesi,18i2, or 



and Selijs Longchamps, Monogr. dos LibuUul! Ann. d. Sc. Nat. XX. 1843, PI. X.-XII.) with 



d'Europe, PI. I.-IV. Ckironomus, Simulia, and Donacia. 



8 See Straus, Consider. &c. PI. III. V. The ulterior phases have been traced by Ratlike 



it See my observations in the Entomol. Zeitung. (^MeckcCs Aich. 1832, p. 371, Taf. IV. and Miil- 



1840; p. 137, and lirulU, Ann. d. 1. Sjc. Eutom. le.r's Arch. 1844, p. 27, Taf. II.) with Blatta 



VII. 1838, p. LIII. The golden-colored tuft orientalin and Gryllotalpa vulgaris ; and by 



of hairs situated at the base of the abdomen Nicolet (Recherch. &c. p. 18, I'l. I.) with the 



with the males of Blaps, does not correspond to Poduridae.* 

 that of Vermestcs, because it is only external and 

 does not project into the interior of the body. 



* [ § 355, note 2.] I am not aware that the conditions of formation belonging to the different 



numerous researches U])on the embryology of the groups, and the observation of the details of de- 



Insecta made within a few years, have added any velopmeut of different internal and e.\ternal organs, 



new phases to the general type of development of Those anomalies of development and reproduction, 



these animals as brought out by the earlier inves- which continued re.warcli shows to be far from un- 



tigators. The type of development with the Arth- common with the Insecta, will ultimately be found, 



ropoda is essentially the same in all of the classes probably, referable all to the phenomena, wo have 



of this section. What late observers Iiave done, discussed below, of the Aphididae. — Ed. 

 therefore, is tlie tracing of some of the secondary 



