351] LARVAE OF THE TENTHREDINOIDEA—YUASA 33 



larvae, but when certain annulets of the segments possess setae their pres- 

 ence on these annulets in successive segments is constant if not in precisely 

 the same number and order. There is a tendency to have more and longer 

 setae on the lower half of the head than. on the upper half. The number 

 and arrangement of the setae are variable on the vertex and front but are 

 fairly constant on the clypeus, labrum, and mandibles. 



A spinal formula is an abbreviated expression of the arrangement of 

 the tubercles or spines on the various parts of the body. The figures of 

 the formula indicate the number of branches of a spine and are arranged in 

 order, beginning with the mesal spine in the case of those on an annulet 

 and with the cephalic spine in the case of the subspiracular areas. The 

 spinal formula of the prothoracic segment represents the arrangement of 

 the spines on the large or second annulet, on the first or smaller lateral 

 annulet, on the subspiracular area, and on the postsubspiracular area 

 respectively. The spinal formula of the third abdominal segment indicates 

 the arrangement of the spines on the first tubercle-bearing (usually 2d) 

 annulet, on the next small annulet if this is present, on the third tubercle- 

 bearing (usually 4th) annulet, on the subspiracular area, and on the post- 

 subspiracular or surpedal area, respectively. 



The number of branches of the spines sometimes varies and the arrange- 

 ment of the spines also may show minor variations. The spinal formulae 

 represent the most typical arrangement. 



Glands and Glandubae. — There are many types of glands opening to the 

 exterior found on the various parts of the body of the larvae of the Tenth- 

 redinoidea. The larvae of the Nematinae and Cladiinae are provided with 

 a series of ventral glands on the ventro-meson of abdominal segments 

 1-7. Sometimes a pair of eversible glands is found in the cervical region, 

 as in Megaxyela major. The larvae of the Cimbicinae possess a spiracular 

 gland located dorsad of each spiracle of abdominal segments 2-8. It is from 

 these glands that the yellowish fluid of these larvae is poured out when 

 disturbed. A peculiar sucker-like protuberance with a depressed center 

 occurs in the larvae of the Acordulecerinae on the sublateral area of 

 abdominal segments 2-4 or 5 and 8. The function of this structure is not 

 known but it is not improbable that it is secretory in nature. The wax 

 glands of the wax-secreting larvae such as certain Tenthredininae, Emphy- 

 tinae, Selandriinae, etc., are minute and located on various parts of the 

 body of these larvae, but their detailed structure has not been studied. 

 The most common type of these glands is found in the larvae of the 

 Diprioninae, Emphytinae, Selandriinae, Tenthredininae, some Nematinae, 

 and others. The cutaneous glands of these larvae are provided with chi- 

 tinized rings about their external openings. These chitinized openings are 

 known as glandubae. They may be located at the end of tubular protu- 

 berances, and in such cases they are spoken of as being stalked, or they 



