28o NATURAL SCIENCE. j,,^^. 



Four days later these larvae pupated, and from the form of the 

 pupa Dr. Chobaut decided that they were beetles of the genus 

 Emenadia. Early in July the perfect insects were produced — a male 

 and two females, of the species E. fiahellata. One of the females laid 

 fertile eggs in the middle of July, from which, early in xVugust, were 

 hatched active larvae of extremely small size, with large head, with 

 a pair of antennae inserted near the base, the thorax with six well- 

 developed legs, and the abdomen of nine segments, the last two 

 being each provided with a pair of long filaments. 



The place in which the female lays her eggs in the natural state, 

 and the details of the transition from the hexapod larva to the legless 

 parasite, have yet to be determined. Dr. Chobaut suggests that the 

 eggs are laid in the earth, and that the hexapod larva attaches itself 

 to the hair of the wasp, which carries it to the nest. The researches 

 of Messrs. Chapman and Murray, however, on the life-history of 

 Rhipiphorus paradoxus tend to the conclusion that the beetle lays her 

 eggs in the cells of the wasp's nest. 



The hexapod larva of Emenadia closely resembles that of 

 Rhipiphorus, as described by Dr. Chapman, except that the latter 

 appears to be without the long filaments on the two hinder abdominal 

 segments. Dr. Chapman describes the Rhipiphorus grub in its para- 

 sitic stage as carrying on its white skin the black chitinous plates of 

 its former hexapod condition, widely separated by the growth of the 

 insect. " These plates," he writes, "may be regarded as a beautiful 

 display of the dermal anatomy of the little active larva." Such 

 plates, however, were not observed by Dr. Chobaut on the grub of 

 Emenadia. In all these beetles we find an active hexapod larva pre- 

 ceding the legless parasitic grub. This indicates that the larvae of 

 the ancestors of these beetles were free-living. A similar hexapod 

 larva is found in some other groups of insects ; from its likeness to 

 the adult Caiupodea it is often called " campodiform." As Campodea 

 belongs to the most primitive group of living insects (Thysanura), it 

 has been held by Brauer, Lubbock, and most other entomologists, 

 that the occurrence of a campodiform larva as the earliest stage in the 

 post-embryonic life-history of various insects points to the descent 

 of our modern insect groups from a campodean ancestral stock. 

 Further, the fact that some Myriapods have but six legs in their 

 early stages has suggested the derivation of that class also from a 

 similar stock. The vermiform insect larva, of which the caterpillar 

 of a moth is a familiar example, has been generally regarded as a 

 form which has become secondarily modified to meet the require- 

 ments of its special mode of life. The pairs of pro-legs present on 

 some of the abdominal segments of a caterpillar have been thought 

 to be not homologous with the six thoracic legs ; and it has been con- 

 sidered that moths, no less than beetles, are descended from cam- 

 podean ancestors. The primitive campodean itself must have been 

 derived from a vermiform ancestor, and therefore the caterpillar has 



