GENERATION OF INSECTS. 405 



multilocular. The sperm-reservoir communicates with the vagina 

 by a short neck in Locusta, and by a longer canal in Acheta. There 

 is no "bursa copulatrix;" and the colleteria are likewise wanting in 

 Forficula, Phasma, and the Acrididce, but they exist in the genus 

 Locusta, and are complex and ramified in the cockroach, where they 

 have to provide the materials for the complex egg-case. 



The ovarium presents two types of structure in the Coleoptera, the 

 flagelliform and the sacciform ; in the former type, there may be 

 either three or six egg-tubes in each ovarium, according to the 

 species. The sacciform type is presented in the darkling beetles 

 {3Ieloe\ and the ovarium is remarkable for the imbricated ar- 

 rangement of its countless egg-capsules. The sperm-reservoir is 

 claviform in Scarabc^iis, or is bent upon itself, with a long neck, com- 

 municating with the vagina, or with the copulative pouch. Usually 

 a simple, sometimes a bifid, rarely a ramified, accessory mucous 

 gland opens into the base of the sperm-reservoir. There are no true 

 colleteria ; and I may remark that these organs are likewise ab- 

 sent in the neuropterous May-flies (^Ephemera) and Dragon-flies 

 (^Libelluld), 



The vulva is a complex aperture in most insects, and is defended 

 by an upper and two lateral valves or plates ; it is usually accom- 

 panied by other modifications or appendages of the terminal segments 

 for grasping the penis and for oviposition. 



Certain social Hymenoptera, which, as John Hunter quaintly 

 observes, "have property to defend,"* possess a peculiar poison- 

 apparatus, which is essentially a modication of those accessory parts 

 of the female organs, which are the only parts that acquire a func- 

 tional activity in the neuters of the bee and wasp. The poison is 

 secreted by two long and slender ducts — the homologues of the 

 " colleteria," which unite together and empty their secretion into an 

 oblong bag, which discharges itself by a narrow duct between the 

 valves of the sting. This is a long, slender, and sharp process, with 

 a serrated edge, which generally prevents its retraction when thrust 

 into the skin ; it is the homologue of the " ovipositor :" the protecting 

 valves are developments of the last abdominal segment. 



The corresponding parts are variously modified in other insects to 

 insure a proper deposition of the eggs. In some Orthoptera, e. g. 

 the Locusta viridissima, the bivalve ovipositor is longer than the 

 body, and, by means of it, the ova are conveyed to the proper depth 

 in the soil, the act of oviposition being precisely analogous to that of 



* CCXLVI. 



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