Yasuhiko Kasahara, author of the website Kay's Beetle Breeding Hobby, has written the following article which describes the captive breeding of Prosopocoilus giraffa keisukei, the world's longest Stag beetle.  Many thanks to Kasahara for allowing me to present this valuable information on my website.  I am certain that many beetle hobbyists will benefit greatly from the techniques discussed in this presentation.

Although the Family SCARABAEIDAE website is specifically about beetles of the family Scarabaeidae, the Stag beetles (family Lucanidae) are in fact closely related to the scarabs and have a similar biology, and many scarab enthusiasts will undoubtedly find the following information very interesting and helpful if they wish to breed P. giraffa and many other lucanid species.

1. Introduction

Prosopocoilus giraffa is the longest of all 1,400 living stag beetle species. My particular concerns are the breeding/rearing of giant beetles, the largest male adult of which exceeds 100 mm in length. As a reference, of all 1,400 living stag beetle species on Earth, there are only 12 species that fall into this category (see the following list: Giant Stag Beetles).

Giant Stag Beetles¹:

   1) Prosopocoilus giraffa (keisukei of Flores Is.: max. 124 mm?); 
   2) Hexarthrius mandibularis (sumatranus of Sumatra Is.: max. 118.5 mm);
   3) Dorcus titanus (palawanicus of Palawan Is.: max. 111.3 mm);
   4) Cyclommatus elaphus (Sumatra Is.: max. 109.0 mm);
   5) Hexarthrius rhinoceros (chaudoiri of Sumatra Is.: max. 109 mm);
   6) Odontolabis intermedia (Negros Is.: max. 107.0 mm);
   7) Prosopocoilus confucius (Vietnam: max. 106.0 mm); 
   8) Odontolabis alces (Mindanao Is.: max. 104.3 mm); 
   9) Odontolabis burmeisteri (S. India: max. 104.0 mm);
  10) Dorcus alcides (Sumatra Is.: max. 102.3 mm);
  11) Lucanus cerves (judaicus: max. 100.2 mm); and
  12) Cyclommatus metallifer (metallifer of Sulawesi Is.: max. 100.0 mm)

These pages present the captive breeding/rearing of Prosopocoilus giraffa keisukei. Discussion on the breeding/rearing follows natural history of the insect, which is thought useful for breeding/rearing. There are 9 varieties of the species Prosopocoilus giraffa²:

   1) giraffa Oliver, 1789
       (max. 108 mm; northeastern India, Nepal, Bhutan, Myammar, Thailand, Laos, Vietnam,
        Cambodia and Malaysia);
   2) borobudor Mizunuma et Nagai, 1991
       (max. 99 mm; Sumatra, Java and Bali Is., Indonesia);
   3) daisukei Mizunuma et Nagai, 1991
       (max. 114 mm; Negros and Sibuyan Is., Philippines);
   4) keisukei Mizumuna et Nagai, 1991
       (max. 124 mm?; Flores, Lombok, and Sumbawa and Tanahjampea Is., Indonesia); 
   5) makitai Mizumuma et Nagai, 1991
       (max. 104 mm; Mindoro and Luzon Is., Philippines);
   6) nilgiriensis Mizumuma et Nagai, 1991
       (max. 102 mm; southern India);
   7) nishikawai Mizunuma et Nagai, 1991
       (max. 104 mm; Tahuna Is., Indonesia);
   8) nishiyamai Mizunuma et Nagai, 1991
       (max. 107 mm; Sulawesi Is., Indonesia); and
   9) timorensis Mizunuma et Nagai, 1991
       (max. 97 mm; Timor and Wetar Is., Indonesia)

Ssp. keisukei is considered as the longest living stag beetle in the world. While a wild-caught male adult specimen of 124 mm is said to be possessed by either a German or Japanese collector, a number of sources say that 118.0 mm is the recorded maximum length of a wild-caught male adult of Flores Is., Indonesia. That means, for beetle breeding/rearing enthusiasts, that the male of this subspecies has a potential of growing up to 118.0 mm long or even longer. In the past few years some breeders in Japan, both dealers and hobbyists, have reported the rearing of males of this variety from eggs to adults of nearly the upper-limit range of 115-117 mm³. The following discussion limits ssp. keisukei, first introducing its natural history and then emphasizing its breeding/rearing methods to win good results. However, this breeding/rearing method can be applied to many other Lucanidae. 

2.  Natural history

2.1  Description: Male 48.5-118.0 mm including mandibles; Female 35.5-58 mm. Elongate, somewhat flat. Dull black with blackish anntenae and legs. Male's antler-like jaws have small teeth along inner edge and a pair of big teeth in the upper middle, and are slightly forked at end. Head of a large male reaches beyond the length of its prothorax and abdomen combined⁴. 

2.2  Habitat: Tropical rain forests⁵. 

2.3  Range: Ssp. keisukei is confined to Flores, Lombok, Sumbawa and Tanahjampea Is., Indonesia⁶.

2.4  Food: The adult saps tree juice and the larva feeds on rotten hardwood trees⁷.

2.5  Life cycle: The insect's life cycle is said to be largely unknown in a natural setting⁸. Under captive rearing (26 degrees C. in summer; 18 degrees C. in winter) of one generation, however, the author has experienced the following:

1. Duration of egg incubation: about 1 month
2. Duration of larval stage:
        Male: 9 or more months (L1: 1 month; L2: 1month; and L3: 7 or more months); and
        Female: 4-9 months (L1: 1 month; L2: 1 month; and L3: 2-7 months)
3. Duration of pupal stage: 1 month

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