42 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I46 



When the aedeagus and the parameres are not separated at their 

 bases, the three parts arise from a common phallohase, as among 

 Coleoptera. In some cases the base of the aedeagus is connected with 

 the parameres by a pair of small basal plates, or again the parameres 

 may be entirely separated from the aedeagus. 



Among the dipterists the aedeagus is known as the "mesosome," but 

 this term (middle body) is not in itself specific for a genital organ. 

 Others use the name phallus, which is from the Greek word for the 

 male vertebrate organ with which the insect aedeagus has no possible 

 homology (and in its ancient usage the "phallus" was particularly 

 an artificial symbol of generation). Aedeagus is specifically an 

 entomological term since the organ has no homologue even in other 

 arthropods. Under the dissertation on Male Genitalia {q. v.) the 

 writer has proposed that the term phallus is a convenient name for 

 the whole genital complex developed from the primary genital 

 rudiments. 



Ovipositor: According to its derivation the word ovipositor 

 should be applicable to any organ used for placing eggs. Among the 

 insects, then, there are two types of ovipositors, one being the ex- 

 tensible abdomen itself, the other special pronglike outgrowths of 

 the abdomen. 



An ovipositor of the first type is present in the tubuliferous 

 Thysanoptera, the Mecoptera, the Lepidoptera, the Coleoptera, and 

 the Diptera. In these insects the distal part of the abdomen can be 

 extended as a tapering, telescopic tube, near the end of which is the 

 Opening of the oviduct. Some of these insects deposit their eggs on 

 exposed surfaces and protect them with a covering of glandular 

 secretion. Others use the extended abdomen for inserting the eggs 

 under the edges of loose bark, or into crevices, or for depositing them 

 in rafts on the surface of water. In some of the fruit flies the 

 greatly elongated abdomen has a sharp terminal point that enables 

 the female to pierce the skin of fruit and insert their eggs into the 

 flesh. A similar piercing tip is found in some primitive moths. 



An ovipositor of the second type composed of movable sclerotic 

 prongs is the organ usually referred to as the insect ovipositor. It 

 is present in a very simple form in the Thysanura but is developed 

 as a complex organ in some Odonata, in the Orthoptera, in the 

 Hemiptera, and in the Hymenoptera. In these insects the ovipositor 

 consists of two or three pairs of closely associated processes sup- 

 ported on two pairs of ventrolateral plates of the eighth and ninth 

 abdominal segments. 



