NO. 3509 SOLDIER FLY LARVAE — McFADDEN 7 



While the quahty of this work is very good, the number of different 

 species investigated leaves much to be desired. In this section, 

 an attempt has been made to incorporate previous work with my 

 own studies in a discussion of the major morphological characteristics 

 of the larvae, both external and internal. 



Integument. — The integument of a stratiomyid larva is composed 

 of many facets, some of which are distincly hexagonal while others 

 vary in size and shape. This faceted appearance has caused students 

 of Stratiomyidae to refer to the integument as being "shagreened."^ 



Many early investigators (Miall, 1895; Leydig, 1860; Miiller, 1925; 

 and Kruper, 1930) noticed the presence of these facets and explained 

 their appearance as representing the upper surface of the "calcareous 

 nails" that are so evident in a cross section of the integument (fig. 6). 

 These nails are composed of calcium carbonate, but how they are 

 formed is unknown. Earlier workers were of the opinion that the 

 calcium deposits were secreted probably by the malpighian tubules 

 in an unkno^\Ti manner. Richards (1951), on the contrary, is of the 

 opinion that the calcium deposits are laid do^vn on the external sur- 

 face of the integument as a result of carbon dioxide diffusing outward 

 through the mtegument into the calcium-rich medium of water. His 

 theory, however, will not explain the development of the "nails" 

 under the acid conditions in which many species of stratiomyid larvae 

 occur, nor wiU it explain the development of the "nails" in terrestrial 

 species. 



The "nails" provide the larva with a strong but flexible armor. To 

 test its resistence to attack one needs only to try to section it. Flex- 

 ibility is obtained by the pyramidal shape of the nails, which allows 

 the integument to bend. 



Head and appendages. — The total length of the head is always 

 greater than the width. This may seem misleading since the head is 

 permanently retracted approximately one-half of its length into the 

 thorax (fig. 3). 



Distinctive eye prominences are situated on the lateral margin of 

 the ocular lobes. Located between the 2 ocular lobes is the clypeus, 

 which is limited by the frontal sutures. At the distal end of the 

 clypeus is the labrum, a structure that is not always clearly defined 

 posteriorly by the clypeolabral suture. The mandibular-maxillary 

 complex is located in the pocket formed by the labrum and the ex- 

 tensions of the ocular lobes. The complex itself is formed by the 

 fusion of the mandibles and the maxillae as the name suggests. It is 

 so articulated that movement is in a plane perpendicular to the long 



'Derived from the near-eastern word "shagreen," a type of uncured leather 

 prepared in that area. As used here, it doubtless refers to the multifaceted 

 integument that suggests this type of leather. 



