826 



THE NATIONAL GEOGRAPHIC MAGAZINE 



One day I had a sudden impulse, or 

 hunch, to put her with a spider and see 

 what happened. Would she attack the 

 spider, and lay an unfertilized egg upon it? 

 Or would she be wise enough to know that 

 it would be wasted effort? 



Somewhat to my surprise, she acted 

 exactly as her married sisters had always 

 acted, paralyzed the spider and laid the egg 

 upon it just as if it had been a fertile egg. 

 F knew that parthenogenesis, reproducti(3n 

 b}' virgin females, was very rare among 

 insects in general, but that it was known to 

 e.xist among a few species. It had never 

 been recorded among the hunting wasps of 

 the Family Psammocharidae. 



So I knew the egg wouldn't hatch — 

 but it did I And that meant that the Pcdi- 

 iiaspis planatus wasp, in addition to its 

 other remarkable qualities, was capable 

 of parthenogenesis: that is, development 

 of eggs from virgin females by self-fertili- 

 zation. 



To establish this discovery, I must be able 

 to verify it by many instances and complete 

 data. So I put Miss Psammy to worls. lay- 

 ing eggs, and added other unmated females 

 as fast as they emerged. I raised more than 

 fifty wasps from unfertilized eggs, and they 

 were all males. So it was safe to assume 

 that the unfertilized eggs of this wasp pro- 

 duced males only. 



Among yellow jackets, parthenogenesis 

 takes place only in the event of the acci- 

 dental death of the queen. Other types of 

 reproduction without mating are found 

 among aphids and gall wasps. But it seems 

 to me that Psammy "s case is a little differ- 

 ent. She seems to be a woman absorbed in 

 her career, the reproduction of the species. 

 And, since she can follow her career alone, 

 it is easy to imagine that she is serenely 

 indifferent as to whether she mates or not. 



If there is no eligible young bachelor 

 available, she should worry! She goes right 

 along, following her destined career and, 

 perhaps, evening up the ratio for the next 

 generation by producing an extra flock of 

 boys I 



"THE CASE OF THE CELLOPHANE SHKATH'' 



And now we must go back to the fall of 

 1935 and pick up The Case of the Cello- 

 phane Sheath (page 813). 



That case was more mysterious than that 

 of the Curious Cocoon. This killer was not 

 known, had no criminal record, was not 

 mentioned in scientific literature. The clues 



left in the murder room failed to give a 

 hint as to its identity. 



The empty shell of the devoured spider 

 indicated that it had been eaten from within 

 by a true body parasite, rather than from 

 without by a "predator" of the wasp larva 

 type. Xor did the pellet of Cellophanelike 

 material tell me anything of value. I knew 

 of no insect having such a pupal case. 



Out of all the thousand trapdoor nests 

 dug up that fall, I failed to find a single 

 adult "mysterious enemy,' alive or dead. 

 The killer had gone, but where? If it was 

 alive, how and where was it spending the 

 winter? How and when and where did the 

 female lay her eggs? Was it a wasp, a fly, 

 or what have you? What did the critter 

 look like, anyway? 



And so the 1935 season ended, conspicu- 

 ous for what I had not learned about the 

 mysterious enemy. 



BEHIND THE SMOKE SCREEN 



Another summer, and a day in August. 

 A great wall of smoke was rolling skyward 

 across the Arroyo Seco. It appeared to 

 come from the direction of our trapdoor 

 hunting ground. 



No pair of happy kids ever chased a fire 

 engine more gleefully than Danny and I 

 raced toward that rolling smoke. And 

 sure enough 1 Many acres of adobe hills 

 were being swept bare of tangled weeds, and 

 the trapdoor season was open again. 



Up the long grade we drove, and into the 

 ash-blackened hills behind the smoke screen. 

 Suddenly I swung to the roadside at the 

 foot of an untried hill. 



"Grab your little broom. Sonny," I said. 

 "I think I have a hunch." 



The warm black ashes lay thick upon the 

 ground. The brooms swirled them into the 

 air in clouds — two clouds, a little one and a 

 big one. The dust settled on our perspiring 

 bodies and stuck tight. But we found trap- 

 doors, plenty of them. I began to dig. \\'e 

 grew blacker and blacker — and then it hap- 

 pened ! 



I broke open a cracked tube and peeked 

 into the bottom half. A weird-looking crea- 

 ture came climbing slowly and clumsily up 

 the silk-lined tunnel ! It looked like a small, 

 humpbacked bumblebee, with a tiny, low- 

 hung head that seemed all eyes (page 821). 

 I let out a wild yell. Danny came running. 



At last! The mysterious enemy! 



During the two weeks that followed we 

 found about 20 more of these long-sought 



