HYMENOPTERA OF CONNECTICUT. 25 



TENTHREDINOIDEA*. 



By Alexander Dyer MacGillivray. 



This superfamily is differentiated from the other superfam- 

 ilies of Hymenoptera by having the cephalic end of the abdomen 

 as broad where it is joined to the thorax as the caudal end of the 

 thorax, never constricted into a narrow pedicel ; by having the 

 first abdominal segment joined to the abdomen, instead of being 

 closely anchylosed to the thorax and bearing a pair of spiracles, 

 and usually with its tergum longitudinally divided at middle ; by 

 the retention in practically all the species of the base of the 

 radial sector; and by the presence in many of the species of 

 more than one anal cell. 



Their larvae either feed externally on the leaves of plants, 

 within their stems, or within the trunks of trees. They can be 

 distinguished from the larvae of other Hymenoptera by the pres- 

 ence of prominent abdominal prolegs, and from the larvae of the 

 Lepidoptera, with which they are most likely to be confused, by 

 the presence of only a single ocellus on each side of the head. 



The most useful characters for distinguishing the species of 

 Tenthredinoidea are found on the head capsule and on the ovi- 

 positor of the female. 



The ovipositor of the female consists of two parts, an ex- 

 ternal flattened plate on each side, and two median flattened, 

 pointed, yellowish plates located between the external plates. 

 The external plates are known as the saw-guides. The variation 

 in the shape of the three exposed margins, upper, lower, and api- 

 cal, of the saw-guides is usually characteristic for a given species. 

 The yellowish, chitinized plates located between the saw-guides 

 are the saws. The distal end and ventral margin of each saw are 

 usually denticulate. The shape and arrangement of the denti- 

 cles or teeth are also usually characteristic for a given species 

 or group of species. 



Contributions from the Entomological Laboratories of the University of Illinois, No. SO. 



